Nightmare. I looked into it when I was short one '52 door, while long on one '51 door for a '52 build. There is a significant difference in the sheet metal where you can't easily get to, and the metal is bent at odd angles. You would need to drill new holes in the door for the newer push button handle and the newer door latch, as well as installing a new striker to the cab. Tiny errors in each of these modifications will add up to a half a mile of error when you try to make that door line up and close right.
I sold the nice condition '51 door I had, ran into a real nice Stovebolter who gave me 2 complete doors in very repairable condition, which I traded to another guy who had a brand new '52 door that I needed, but was missing the other door. I got the door I needed and he got two very restorable doors.
High end horse trading went on right there.
