The Nortwoods event is an "all Ford" powered-only event and involves hogh speed track "touring" as well as a high speed autocross on Saturday. The traditional date is the weekend after Labor Day in September. However, this year's event is held on August 27-29th.
http://www.nwshelbyclub.com/
You can enter the pits with your car for free. Just touring the massive and scenic infield is worth the drive in itself.
If you can make it, you must!
/Randall