This swap works if you start with a newer 14 bolt Dual Rear wheel axle from a cab and chassis. then you install single rear wheels on it.
It will not work if you start with a single rear wheel axle, well not and fit the wheels under fenders on a step side pickup bed..

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-