David Root:
FYI The "Oval, larger scale and more" forum has a "1/10" thread that is 1/10 scale GTP roadcourse pan cars. These guys are out of SoCal raceway and are a very active group for this class! Mark A is the group ringleader and knows ALOT about these cars and I race with him often. These guys are active supporters of this class and will be very happy to help. Any advice from the more active members, MarkA, Thirdplace,Colin,Boomer is good info!
I only race stock with my Associated L2, but they also race mod as well. Here is the most common gearing for SoCal, which should be a fair starting point:
P2K - 18-19 x 84
P2K2 - 17-18 x 84
Monster stock 15-16 x 84
Don't remember off the top of my head what that comes out to in roll-out, but most of us use a full-size tire....our track just seems to like them better than a smaller diameter tire.