A fellow Stovebolter found a 1954 2 ton NAPCO 4x4 conversion. He swapped the 4x4 stuff into a 1951 6100, bolted right in following original NAPCO install instructions.
I'll try to find some pictures.

Otherwise you're probably better off forgetting about 4x4 or finding a different newer 4x4 vehicle and just using it as is.

•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
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-