While I have shortened some axles and it does work it's not simple....
Another I think better way to go about it is adapt newer spindles complete with the related disc brake components to an original axle beam. This can work great and works better on dual wheel trucks than single, but won't work in all cases because of the measuremnts, you need to check.
Here's the info.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=725027#Post725027

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-