As for tire size, you can run 195/65's on the front, and 205/60's on the rear. Chuck and my father are big fans of the "tall and skinny" tires, but I like to have some meat on the road.
There are a few pictures of Chuck (floating 'round the net) at 136MPH at the salt flats. You can see the dust roilling off the rears, and the fronts seem to be about 1/2" in the air!! I also remember when Pat Downs drove Bob's turbo spyder at the Run and Gun. Chuck asked him how he liked it at speed , and his response was something like... there's no point in holding the wheel, 'cause the fronts aren't on the ground!
We've done a few years worth of testing/tweeking and have made an aero kit for our track cars. Last year, we hit a hair under 300KPH at Interlagos... not too shabby for some bolt on aero mods.. It is fugly, but in a way that makes me LOVE it.
I'm glad you're playing with one of our spyders Jake! I think you'll even surprise yourself with the power/performance when all is said and done! AND this is going to make one HELL of a car for someone!!
Carey