Few things to consider...

First off, what's your bolt pattern? I'll assume 6 lug Budd stud centered??

Second, tire size depends on what width wheels you have, and there are different wheel widths available.

For a lot of info check out our wheel and tire tech tip, not all of it covers your wheels, but still a lot of info will be helpful.
You'll find the most helpful info in the Accuride Wheel catalog, linked in the tip. In it you'll find the part number for new 6 lug Budd 22.5" wheels, as well as recommended tire sizes for given wheel widths (page 39).
http://www.stovebolt.com/techtips/wheels/

Used wheels are also easy to find, and can be much cheaper than new even after blasting and powder coating.

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-