I didn’t catch that earlier, I’m with Jerry and they should be 1/2-20 thread.

The truck in question should be stud centered only with some room between hub and wheel center bore. However if you get new wheels there’s no harm if they do fit hub snugly.

•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-