Hi Josh:
Lucky for us a lot of Vipers and Porsches use those same 17s and 18s so there are a number of tire options. None of them are too cheap, though...
Call those guys noted in my prior post - Vance at the Tire Rack and Vaclav (pronounced "Vas-Lav") at Carroll Shelby. They're both really good guys and very helpful.
Let me know if that doesn't help.
MM
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