I put the subject tire, Avon CR6ZZ's, on the GT40. The tires are extremely good, that opinion formed after a few track days. Although tread depth isn't much, tire wear wasn't measureable. They stick great, don't dart and provide a reasonable ride for a race tire, which softens the financial blow . . . them suckers are expensive. Check out SASCO's listing for Avons.
Tire Specs :: SascoSports
I installed 225/65R15's front and 295/60R15's rear. The wider 245/60R15 wouldn't work on the GT40 due to its height, but no problem. Handling was neutral . . . no tuning necessary. The 245's should go on a Cobra, though.