I be cautious with the bolt on disc brakes commonly used by the 4x4 crowd. I’m not convinced those parts are that great for a 1 ton truck used as a truck, they’re likely popular because it’s easy and not because they’re the best option. See more brake choices and ideas in the 14 bolt swap sticky thread.

Before swapping later model drum brakes measure and see if they will swap, several different spacings between hub and backing plate flange exist, and drum to hub details.

Before putting disc brakes on the rear you should put them on the front anyhow.

•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-