The NMRA is having a class that is NA. The rules limit to a stock suspension though. The rules are at
http://www.nmraracing.com/hotstreet.html
Another note: The World Ford Challenge had a NA heads up class in 98 and they got rid of it for 99. I believe that it was due to the number of competitors? They had a good payout for this class and not a lot of cars showed. I love NA cars and would love to see them run. I was looking forward to seeing the Super Trooper and never got to see it.
NA cars rule!!