Gene,
Do you currently have Dayton Spoke type wheels on your truck? If so all you need to do is source Dayton 22.5" rims from your local big truck junk yard. The center part of the rim is the same as the Dayton 20" wheels so they will interchange right onto your truck.
Check with your local school bus repair garage for used tires, they don't run worn tires and you may find some good used ones cheap.
Mike B
