If you're going to seriously autocross (not like what I'm toying with--just going out to test the car's traction limits and learn how it handles), then having a second set of 17s seems like a great way to go. Even sticky 15s are not going to handle like ultra-performance low profile 17s.

A little plug: Troy's got a nice looking set for sale ;)

I just put 18's....285/40/18 rear (27" diameter tire) and 245/45/18 front also 27" it may be better with a 26" tire in front, I did have a little rub to sort out..

In the past 7 years in this order on my B&B Cobra all 15"
BFG---MT S/R----Cooper Cobras----Avons
BFG- hard and slick

MT S/R--- Sticky for a street tire, did not like the flex in the sidewall

Cooper Cobra---not quite as sticky as the MT but good. wide grooves--- Nice stiff sidewall--very nice all around street tire---just ok for autocross, had to be careful around cones

Avons---$$$$---Sticky 60 on the durometer---stiff sidewall---nice 15"autocross tire---Narrow grooves ----Great on the street---nice clean look

Great comparison! Thank you!

Can you comment on the predictability of each, i.e. did any of them stick then give way, or are they predictable and progressive?

BFGs had a few years on them so they were hard. Great burnout tires and easy on the drivetrain but wouldn't hold the car and with a 30lb. flywheel keeping the wheels spinning- downright dangerous. predictability ---yup---- right from the start. Sent me in a 360 in the autocross faster than I could recover.

MT S/Rs were good in a straight line but I tended to feel the car wiggle and sway slightly, they were sticky and made noise before letting go so I would say predictable. I did not Autocross with these tires.

Cooper Cobra let me know very slowly that they would slip and did so, however I could predict the slipping on cornering and powerslide through it--not exactly the fastest way around but I learned alot while doing so. They were a good burnout tire with a little more effort with my right foot and pulled you back in the seat.

Avons Sticky Stick Sticky for a street tire. I am still learning the slip angle and breakaway of this tire. It is testing my courage and learning experience but my car in the Autocross picked up several seconds. I'm still learning how far I can push these tires and myself, but its good knowing I have the tire under me. I've noticed they make very little noise compared to the others when cornering. They don't do great burnouts like the others as you move forward quickly, but I have moved away from this entertainment and since I don't care about the burnouts anymore I changed to an aluminum flywheel which really made the car quick in reference to accelerating and decelerating. This year I put more gear in the car. This should be fun.

I knew this was going to happen--dam disease--I have completely rebuilt my car in 7 years. Whats next.. a trailer?!

Great information. Thanks!

Went with torque thrust wheels and falken azenis 615k.

Thanks for all the advice guys!!!!!!!!!

Sooo many choices
 

For 17's you may want to look at Factory Five's 17x9 and 17x10.5 wheels. They are reasonably priced. I think you can get them from ?Trico? as well.
For tires I briefly had Nitto NT555s, 300 traction compound, but they were not sticky enough for 570 HP. Went to Nitto NT01, DOT compliant road racing, 100 traction compound, which are as sticky as anything that is DOT approved. Factory Five recommends Toyo R888 which is similar to the Nitto NT01, in fact they are sister companies. It is important to note that neither of these tires are suitable for the rain.
Hope you find something that works well,
Mark