Take a look at the BRL rules listed on the oval section under "BRL" for the brushless pan car stuff. You're correct- in pan cars, it's four-cell and either the 13.5 or the 4300. 4300's, on a 90' runline will be very quick- I'd say it depends on your drivers. Looking with decent to good club drivers at 100+ laps in five minutes (BRL is five minutes, and easily attainable) I'd suggest sticking with the BRL style of rules, as it's quickly being adopted as gospel, at least in the midwest. For the sedans, can't help ya there...