Saw your smiling face on the Optima Challenge I re-watched last night.
Go over to
www.corvetteforum.com go to "general corvette" and then to "auto cross and road race" section. You can find scubs and low heat cycle A6's and R888 cheap...maybe $75-$100 a tire. they come up pretty often in 18 inch sizes. You should be able to find the guy that deals in them and talk directly to him.
From what I have read over there you will need to run a lot of camber to keep from cording the edges of the A6 and R6. A-is for auto cross and soft compound and R is for the big track. Takes heat better but harder. Just like stated above most run the A6 for qualifying or time trial runs.