You can find some 22.5 wheels, but it will take some looking.
They were only made for a few years, starting in 56 and only on the 1.5 ton, the 2 ton that year had 6 lug.
I have a set for my project, check my picture link to see some, they are near the end of the Detroit album.
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-