First, if you have not already browsed this thread and the links and tech tips contained in it you may find some of your questions answered. https://www.stovebolt.com/ubbthread..._and_tires_---_What_to_d.html#Post867617

To put some diameters/numbers to this:
Original 8.25-20 tire
~38.3" diameter

8R19.5 tire, about the tallest (without being extremely wide) 19.5" tire, also fits on the available 10 lug 19.5 wheels.
~33.5" diameter

9R22.5" tire, as narrow as is available for the 22.5" wheels with the 10 lug on 7.25" pattern.
~38.5" diameter

The suitable/available 19.5 tires are 5" shorter than the original and the suitable/available 22.5 tires.

likely no ready made bushings/rings for the later wheels on the early hubs because demand is so very low.

•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-