I am going to do this on my 48.
It seems basically simple except you need to find and weld in place the inner brace/reinforcement from a later door.

Here is a picture of those two braces still stuck on a piece of old door skin. (also shown some unrelated cab mounts)
https://picasaweb.google.com/lh/photo/E1VEEF5aDBq6zJLbZRxDx9MTjNZETYmyPJy0liipFm0?feat=directlink

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-