Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!
Congrats, and you've got the fasted color. Glad to hear you're going to track it, like it was built to be used.
Are the GT500 wheels 18"? If so, I'd suggest using those for track duty because of more tire choices. If they're 18x9.5, you're in great shape for 275 or 285 width tires. If 18x9, then you'll have to use a slightly narrower tire per tire manufacturer recommendations.