The wheels on larger trucks are 10 hole hub piloted and a few 10 hole Budd type left. Yours are 6 hole Budd type or what we call ball and seat. The inner wheel is held with a stud which is the ball and the seat is the hole in the rim. The outer wheel is held by a 1 1/2 wrench size nut which is the ball and the wheel being the seat. GM offered tubeless with 6 hole Budd probably beginning in the late 50's. So they can be bought in salvage yards and probably still new. A 22.5 from a semi is supposed to have an 8.25 width rim. However, many are mounted on 7.50 rims, especially on farm trucks. The size should be stamped on the wheel or you can measure the rim width like this.. http://resources.coker.com/wheel-tech/wheel-installation/how-do-i-measure-my-rim-width.html
The 2 common sizes today are 11x22.5 which is the same diameter as a 10.00x 20 and what we call a low profile 22.5 which is the same diameter as as a 9.00x20. The low profile are by far the most common and have the load carrying capacity of a 10.00x20