This is what a 14 bolt swap takes.
https://www.stovebolt.com/ubbthread.../14-bolt-axle-swap-info.html#Post1249600

Another larger 5 speed Overdrive that can be made to fit, but more expensive and little more work, is the NV4500. Some searching the forum may explain that process.

It’s very likely that you could use modern drum brakes from a 14 bolt on your original Eaton, as yet another option. I haven’t researched this enough to know just what’s required, but I’d bet it’s possible and not terribly difficult.

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-