Dragging this up from my archives: Mustang II crossmember build up I feel there are two different types of cross members available. I will group them into the Heidts style and the Fatman style. There are multiple manufacturers of both styles with the majority of them being the Heidts style. This is the one I am going to focus in on as the Fatman style has a few inherent problems and to correct them you end up with a Heidts style crossmember. The Fatman style crossmember does not support the frame rails and relies on frame rail torsional strength to hold the spring towers in place. Few guide lines here; Mustang II has a stock track width of 56". If you use the brake rotors from a Ford Granada your track width will be 58". I will go into brake conversions later, more importantly we need to establish if this is the right choice for you. If your car or truck is wider than 58" it is possible to widen the track width, but with a loss of correct geometry and a degradation of handling ability. Widening the rack and pinion with rack extensions will wear the rack out faster because of the increased load. The farther the pivot from the support bushings the more strain is induced. This is also best suited for frames under 30" wide overall. If you have a wider frame such as cars from the late thirties to early fifties like Buick, Oldsmobile and Cadillac that have a 58" track width and a stock IFS but have a wide frame it may be necessary to build a new frame clip that narrows at the axle centerline. I have done several of these in the past with great success. And at that point you have the advantage of building some drop or rise in the frame to adjust the final ride height. STUFF YOU WILL NEED There are some variances here, use your best judgment. Safety equipment is a must! Eye protection, ear protection, good welding gloves and a quality welding helmet. You will need a 4X 4 sheet of either 3/16" or 8 gauge steel. I prefer to use 10 gauge cold rolled. It is easier to work and lighter. It also requires you double up in the upper spring pocket, which makes the kit a little more complicated so I think for simplicity we will stick with the heavier material. Cold rolled steel is cleaner and stronger material, and more expensive. An alternative is to use pickled and oiled steel, PO. The main reason for this is the elimination of the hard mill scale, that black coating on the sheet. It is an impurity from hot rolling the sheet not unlike what happens to steel that you heat red hot with a torch and let it cool, it forms the same thing. That stuff is hard like wedding day dick and a bitch to grind off. When it comes to finishing your welds that scale will wipe the edge off your sanding discs almost immediately. You will need some tubing or pipe 3 ¼" in outer diameter. Two pieces about 2" long is all you need. You will need two beveled washers; I use the radius arm washers from F150s Also handy will be heavy paper or poster board. Corrugated cardboard will work but is harder to cut cleanly. A compass, graphite pencil and a silver pencil or soapstone, straight edges and scissors to make your patterns from. You will need a way to cut the parts out of the sheet. If youre really hearty you could use a jig saw but that is a butt load of work and noisy as hell for a long time. Most of this will be geared toward using an oxy/accetlelene torch. Once you have the parts cut out they will need to be finished. The best tool for this is an angle grinder with a sanding disc. I use a 4 ½" X 7/8" 50 grit aluminum zirconium sanding discs. These discs are more expensive than aluminum oxide discs but last about three times longer. You will need about a dozen aluminum oxide discs or four zirconium discs. A drill press will be handy but not necessary, a 3/8" hand held drill motor will work but a ½" drill will be better. You are going to need a ½" and a 5/8" drill bit. A die grinder with a carbide bit will be helpful for making the slots for the upper control arm slots, but if you dont have one a handful of files will work. Lets get started. To keep this simple I am going to be thinking of a car like a 1935-1940 Ford or 1949-1954 Chevy. These are about the simplest frames to deal with, each having their own quirks. Mostly we will concern ourselves with the construction of the crossmember and getting the geometry correct. Support the car off the ground and level it out as best possible. Tree stumps and large blocks of wood work fine. Good quality ratcheting jack stands are good too. I fabricated some non-adjustable stands about 20" tall, makes it easier to roll around underneath on your creeper. Strip off the front old suspension; advertise it on the HAMB classifieds. Remove any existing cross members or brackets that are going to be in the way at the axle centerline. At this point I would leave the front fenders on, if you already removed them mock them back on. Take a tire near the size you intend on using and set it under the fender at the ride height you want. Notice for and aft placement, sometimes the stock location is not the best aesthetically. I try and sneak the wheels forward a bit on cars and trucks I intend on really slamming down look better to me. I would always err on placing them forward of the center of the fender well instead of rearward. Keep in mind scrub lines and usefulness. Hammering it flat out may look cool, but is hardly practical. I try and set at least four to five inches of ground clearance. Once youre satisfied with the placement of the wheel(s) measure up from the ground to the center of the wheel this is your spindle center, and from the front edge of the door or other reference point for the for/aft axle centerline placement. At this point you can remove the sheet metal. Use a long straight edge and set it on top of the frame rails. Place it at the same for aft dimension for your axle centerline. Also if your spindle center is on the frame rail go ahead and mark where it is in relation to your axle center. The rack and pinion is going to be about three inches lower than your spindle center if you are using stock spindles. If your spindle center is higher than the top of the frame rail you may need to run dropped spindles. Generally the spindle center is two inches below the top of the frame rail for a standard installation. Two inch spindles will allow you more engine clearance if space is an issue. If not you can push the crossmember up into the frame, remember that you may need to raise the engine this same amount. That may involve installing a new transmission tunnel. If you intend on installing air bags and want to lay frame this may not be a bad idea. Otherwise it is a lot more work than I care to do, spindles are cheaper than my time to install a new floor tunnel. Now that you have established where the crossmember will go, box your frame rails. For the Chevy guys with the top hat shaped frames, you will need to box the bottom of your frame. They only have thin sheet metal there and it is very prone to rusting through. Take some of your poster board and lay it up against the frame rail, trace and cut out. When you transfer the pattern onto your sheet of steel make the pattern slightly smaller than the frame. This will make it easier to weld and give the weld bead a place to go. IF the boxing plate is the same size as the frame rail or bigger you will not get a good solid weld and it will crack out. Finish grind and sand to your taste. Transfer your axle centerlines all the way around the frame rail using your long straight edge. They need to be parallel from side to side. Your frame rails may not be parallel to each other so dimensions made perpendicular to the frame rail may not be accurate. Measure 1 ¾" in front of and behind the axle centerline and mark the frame at these points. This is where the front and back plates are going to be at. Measure the inside of the frame rails at these points. These are going to be the outer edges of the vertical supports for your crossmember beam, draw these out on your cardboard. What you want to do is re-create a cross section of your frame rails. So go ahead and locate all four sides of the rail, top bottom and outsides. It is best you draw this out in the center of a large piece. Cardboard is cheap or free so use it up. Also locate where the spindle center is in relation to your frame rail. Now measure down from spindle centerline 3 ½" (stock spindle) or 5 ½" (dropped spindle) on both sides. This is going to be the vertical dimension (ref. drawing 1, dim. A) for your lower control arm mounts. These mounting holes are going to be equidistant from the center of the crossmember and 21 ¾" apart (dim. B) and the holes are ½" in diameter. You can draw the upper and lower parts of the main beam at this point making the lower control arm mounting holes the center of the beam. The beam should be about 3" tall at the most. Now depending on what style rack and pinion you are going to use and what your needs are depends on where and if you drill holes for the rack and pinion. Most of the time we wont drill them out just mark them for locating rack and pinion. For stock Mustang II rack and pinions, power or manual, the first hole is 2 1/8" (dim. C) from the left (driver side US) and the second is 16" to the right (passenger US) (dim. D). If you plan to use a power rack from a Fox chassis Mustang, Thunderbird the second hole (dim. D) is 15 ½" over. To finish the front and back plates draw your inside vertical supports from the top of the frame rail down to the main beam. The intersection points should be 18"+ apart (dim. F) for the best rack and pinion clearance. When youre done it should look something like drawing one. Now the fun! Cut out your patterns and transfer them to your plate. I center punch through the pattern to locate the control arm holes and rack mounting holes. Use soapstone or other heat resistant marking device. Fire up the old blue wrench and get cutting (or jig sawing for you HE-MEN) I leave a little extra material when cutting with a torch, even with a straight edge guide the line I cut can be a little jagged. Once youve cut your pieces out clamp them down, or in a vise and grab the angle grinder and grind down to your lines, make them all smooth and clean. Then drill out the lower control arm attachment holes to ½". Now you will need a pair of tubes 3 3/8" long with a ½" bore or larger and a pair of 1/2'" bolts or all thread and some nuts and bolt the two pieces together. Starting to look like something isnt it! Check it for fit in your frame; it should fit up nicely with out too much gap to the frame rails. Once satisfied with this part cut two pieces of plate for the top and bottom about 18" X 3 ½" and two for the inside vertical of the crossmember. Clean up your edges of any slag or grinder dirt and tack the bottom into place. I recommend making some internal gusseting near where the rack and pinion bolts will be if you plan on mounting the rack straight to the crossmember and not rotating it back. These will act like a crush sleeve and keep over zealous wrenching from collapsing the crossmember. Tack welds the top three plates into place. Now suit up and weld that sucker together. Sit back and enjoy a cold beverage and admire your work. When the crossmember cools down, grind off the ugly and finish to your taste. Now lets tack that into the frame. The frame should be level at this point. Slide the crossmember into place and center it on you axle center line marks. The crossmember should also be level. Check to make sure the frame is square by cross measuring (diagonal) from holes in the frame and double check to make sure the crossmember is where it is supposed to be. Weld it down. Part two coming soon. I will post the images at the end of the thread.