Added 1957 Airbox Corvette

Added the 1957 Airbox Corvette. These cars were equipped with both (Regular Production Option) RPO684 which included the heavy duty brakes and suspension, and RPO579E, which included an airbox which increased horsepower by capturing cooler, higher density air, forcing it to the fuel injectors; and additional hosing ducts to cool the rear brakes to restrain the performance when necessary.