I converted a 57 3/4 ton to a 4x4. I used a 1981 LWB Chevy frame. The frame widths are exactly the same, 31.5" if memory serves me correctly. I had to shorten the frame by 10.5". I welded 3/8" steel, diamond shaped, gussets on the inside of the frame, as well as butt welding the frame where I made my cuts. I mounted the bed flat to the 81 frame and let that elevation be the baseline for the height to mount my cab and fenders. I mounted the original cab mounts from the 57 frame to the 81 frame. The rear mounts mated flush, but i had to build some reiforced spacers to go on top of the front cab mounts. I also had to fabricate spacers to mount the core support. This all sounds complicated, but it really wasn't. The transfer case shifter came up perfectly in the cab. I also had to have the drive shaft shortened and balanced. The 81 frame makes a dip down just behind the front tires and that's where fabrication is needed to support the front of the cab. Give me your email address and I can shoot you some pictures if you like. It came out really nice.
