You need 17" minimum up front to clear the brakes. You can go 15 or 16 in the back (look up Bogarts). However, why not just get a set of take off wheels from a stock GT? For just a few hundred buck + the drag radials of your choice out back, you've got a bargain set of wheels/tires for the track. That's the route I went. Of course, you could do a set a Bogarts (big & littles) and spend $2K, $3K, or more for the set up.