I don't have the answer you want, but keep in mind the ride height, brake package and wheel offset will come into play too. What works on a car with a disk brake conversion (often adds track width) or a straight axle moved slightly forward might not work on a stocker....I would specify your set up
Mount up some small rollers and set it on the ground, then take measurements at lock-straight-lock positions, there are so many variables, I doubt the header company can even suggest a size. Godspeed MrC. Lets see this thing! post some pics.
Thanks, I know I need to do mock up but my heads are out getting done and I jumped the gun and bought 205-75 -15 for front just hoping they fit. I will get some picture on as soon as I get time. 454 will be in stock position. and I'm not afraid to heat n beat, cut n weld!