Back at it, got the entire box disassembled ready for measuring. Also picked up a complete 59 GMC front clip to replace some bad parts on mine.
This photo is one I found on line
This is my crude cut and paste to show the mods. I'm thinking the box is too short, I may not make it a complete short box. Take the full 12.5 "out of the back and only 3 or 4"out of the front?
I was just about to suggest doing it that way. I'm curious, is changing the overall length so it'll fit on the newer Chevy truck frame?