John,
I replaced the small window cab on my 59 chevy with a big window cab from a 58 GMC. I also did the dash swap and it wasn't that bad. Like everyone is saying there is a lot of pinch welds to drill out. I would also make sure that it is on a flat surface when doing the swap. The cab remains ridgid but im sure there is a chance it could twist a little.
The cab i purchased was from a 1 1/2 ton GMC so there were a few more holes in the firewall that my body man plugged and welded for me before he painted it. At 40.00 per hour I think i should have waited for the right 59 cab to come along. Fortunately the hood hinge holes were the same. You will need to change them if youre using the 58 front clip. One other small thing was the transmission cover plate. The hole for the four speed on the GMC is a little off from the Chevy.
Good luck.
Brian M
