Depends on tire diameter. I would use MT ET Street Radials. If you have a 17" rims up front, go with a 25-26 overall diameter to stay in the same range as the fronts. S that would be something like a 250/50/15 or in that area.
If you want to really hook up go with some Hoosier slicks. But your going to need a entire new set of rim because there is no way your going to want to spend the money on the slick then drive them on the street you'll replace your tires like every two weeks. If you want some tire that'll work on the road and have a decent hook up on the track go with some Nitto tires.
No Kidding it's raining here in longmont tonight and my dad had to drive the GT home and that has nitto's on it. We had to keep it at a low RPM and stuff so it wouldn't slip but it wasn't so bad. Looking forward to is snowing.