OK, I'm following a little better now.

For determining how and if brakes swap measure and compare the distance from backing plate flange on axle tube to back side of hub where the drum mounts.
For example the 13x3.5" deep drum as on my C&C 14 bolt needs 5-15/16" to fit the whole brake package. Or with shallow drum needs 1-1/4" less.

I'm reasonably certain that only one backing plate (one offset) is available for each shoe width, if this is not so I'd like to learn more about it.

The original 1 ton AD rear brakes are 14" X 2.5".
To use 13" X 2.5" is a step backwards in stopping ability.

I'm looking at brake swaps/upgrades to get more stopping ability to cope with higher speeds and or good sized loads.

Grigg

•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-