Here's what I am seeing after thinking about this most of the day. Most times I've built an av8 I start from the front forward using a unsplit 32 wishbone and crossmember, than fit the engine and trans to that. You engine looks further back than any I have built. I've also never tried to build one from the rear forward with an A axle like you. Looking at my own pictures, I would say my engine is roughly 1/2 - 1 inch further forward than your engine currently. Can you get you passenger head off in it's current location? That's a pretty good tell for if it's aligned "correctly". If it's to far back it's under the firewall and you can't get the head off in car. If you move the engine forward enough that you can get the head off, Clearance at passenger firewall and head will still be very tight, then your next thing I would look at is the front pulley to crossmember clearance. It should be very tight as well. Just enough room to slip a belt in and out. My motor mounts are made of square tube, but I definitely know the leading edge of them is slightly over the lip of the front cross member. My fan looks closer to the radiator as well.
There are a few things that I would do. It looks like your fan is to far back from the radiator. You want it closer so you don't run into overheating problems later. I would move or modify the engine mounts forwards and lower an 1/8 or 1/4". If you have the wheels, tires and front axle you'll be running installed, set the carb base level, that will tell you if the front of the motor needs to come down or up. I would disconnect the torque tube at the tranny and make the motor fit, then worry about putting the rear axle where you want it. You can make several 1/8" or so adjustments to get where you have the clearance you want.
I just went out and took a pic of where my front mounts are tacked in. This is my first fendered build. I'm 11/16" from rear of crossmember to front of mount. As I stated, this is a fendered car and the engine needs to land just right. I also spaced the mounts 1/4" down from inside top of frame rail. There is just enough room to sneak in a spoon pedal on firewall and filler tube will need to bent a touch. I know all this is irrelevant as the OP is using an A axle, but thought It would give an idea where mounts are in comparison to the photos posted by OP.
So what are the pros and cons of moving the body back a few inches rather than recessing the firewall? I've got a '28 roadster pickup and will use a stock pickup bed, but don't plan to run a hood or fenders.
I think the 2 biggest issues are, (at least for me) 1- I used the original A rearend, and 2- I’m running my fenders..... so,since the original rearend top leaf is beveled, to match the bevel in the crossmember, no amount of moving the rearend forward will work, as when you bolt it back in, the beveled leaf/crossmember work there way back to the spot Henry originally placed them, also I wanted the wheels to be centered in the fenders as I’m using Cheater slicks that “poke out” an inch past the fender. So with the rear in place where it is, I bolted my trans to the torque tube and worked forward from there. The spacer on the clamshell, lengthen the driveshaft/tube, reverse the firewall, or like I did modify the firewall is the only solution I was able to came up with. Heating and/or ball peening a clearance area will work, but I had a welder and broken handled shovel so I did that as it’s a smooth transition and hard to tell (except that I have the clearance) that the firewall is modified at all. Again, this was just my experience.
The top leaf, and the crossmember are beveled (at least mine are), so trying to move the rear forward will just put it back to the original spot as the U-bolts are tightened back down, as the bevels mesh back into place. The only alternative would be a narrower spring, but then it would be able to move around in the crossmember cavity.
The Jalopy Journal
