SRX7: The Cars
The rules are designed to keep all of the cars equal. With the exception of a few specified upgrades, SRX7's are basically bone stock 1981-1985 Mazda RX-7s. Unless the rules specifically say you're allowed to remove, replace, or modify something, then it must remain the way the car came from the manufacturer. The complete rules can be found at 2008 Spec RX-7 Rules
