I have 15x7 rims for track tires with Hoosiers and 16x7's for street tires. The hotshoes with GSLSE's typically run 13x8's so... I admit that I never plan to go beyond local area. Oh, I have 205/45 tires (track tires might be 205/50). The national level guys are running 225/45-13's on a GSLSE. I couldn't really tell you what the SP or SM guys are doing for the TII's. I don't think the added gearing of the smaller diameter is that important to you since your car has more torque.

If you are running stock class the usual is to get some street rims in the size you like and use your original rims for track rims, but I am guessing you already have enough mods to take you out of stock...