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