you can run slicks and you will be fast the down side is you will be put in a racing tire class and you'll prolly get yer ass kicked, As for wheel size I personally run Falken Azenis 245 45 17's. I give up a little to the guys runnin the 15's though.
I second that!
If you use slicks, you will go up against cars you have NO Chance of competing with.
Just stick with what Steven suggested!
I like my Kumho's, but they are more for performance on the road, rather than autox. They are Z rated!