I have not done this, but I do know that '63 was the first yr. of the "ladder frame" design that GM contiued until '87 The cross sills prbably just have different mounting points on '60-62 than a '63-66, but there's height to worry about too, I just don't know. I agree with Scott 'cuz here in the land of salt and more salt I find pristine sheetmetal a beautiful thing making any retro efforts worth it! I once built a pick up box trailer with the back 1/2 of a '63 c20 and I had to cut and weld a lot of bed iron to make the cross sills solid, esp. the rear one. Also welded black iron pipe to the rear sill to accomodate the 2 rear frame bolts. Rust, rust rust!
