First you need to say where you'll be positioned? On a straight? On a corner? If on a straight, you need to brush up on panning. Trusting to high shutter speed may not cut it.
Whatever, use the fastest aperture you got so the background (combined with panning) nicely blurred. You'll be too far away from the action to get any part of the car out of focus.
2nd, how far away? Out of the paddock and you can be quite some distance away from the action. If unsure, best bet is a zoom, the longest you got.
Thursday sounds like a practice day? In which case - pack a wide angle as well, for those 'arty' car shots and up close driver shots
Have fun