Your bolt pattern was somewhat limited in use, I don't have the year range handy..
No, not any GM truck, just the ones that share your bolt pattern. Take your tape measure or calibrated eyeball.
Any bus that might have had that bolt patter would be quite old, I think better luck hunting in the junkyard.
22.5" truck tires are as readily available as they get. You're probably looking for 10R22.5 as first choice, possibly the smaller 9R22.5
