Paul Gage tires for Spirit Reynard?

I have a Spirit Reynard off of Ebay that I haven't run yet. My Girlfriend's Son In Law has the car in Pennsylvania and says it "Totally rocks" on his track. It has urethane tires on the rear (That's why he took it to test). Cathie is dropping by in about a week and a half and will bring the car back to me. I am sending in an order to SCC on Tuesday, with some stuff I need right away. Has anybody put a Paul Gage tire on one of these cars? What size tire would fit it? If nobody knows, I'll just measure the wheel when I get it back and select a size. I can always wait until my next order. I tried to talk him into measuring the wheel, but his reply was, "Gee Pops! I'm a veterinarian, not an engineer!" (He doesn't have a micrometer in the house) The wheels are the stock ones that came with the car, so there should be no surprises. Spirit is not listed in the Paul Gage Tire finder on SCC.
Thanks!
Dave
Thanks!
Dave