1/2 and 3/4 ton axles are all different parts, but they are swappable as a whole assembly because same spring size and spacing. If for whatever reason you wanted the 1/2 ton front axle in a 3/4 ton truck or the reverse.

•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-