Doug,
The 6-lug 22.5 tubeless Budd wheels were used on school buses into the 1970's, so start looking at the old buses in your local junk yards.
The 9x22.5 tubeless tire is the equalivalant to the 8.25x20 tube type. If you put 10x22.5's on the rear you'll get a little more top speed as they are taller.
Mike B
