Just like FrankM mentioned earlier - we run .90 index heads up pro tree classes from 8.90 to 12.90 - All are no electronics, no throttle stops.
10.90 and quicker can use transbrakes - 11.90 & 12.90 are footbrake only.
We've been running these classes for the past 10 years. Car counts vary by class with 10.90 being the largest. We've had fields as big as 34 cars in 10.90 and as little as 4 cars in 8.90....
For some reason, 12.90 seems to be a very low car count - you would think that it would be one of the largest fields as it's a fantastic class for entry level racers.
Our series also runs an open comp and pro comp class (1 tenth breakout allowed) and some of the index racers run both their index class and one of the comp classes.
www.raceosca.com - see schedule and bring your cars up for some fun!! We get quite a few racers from western New York.