Total production for 1966 was 1,373 fastbacks, including two prototypes and four drag cars, and the 252 early production models with Ford Mustang 1965 bodies. In order to help Shelby sales, Ford, the major shareholder of Hertz, persuaded the rental car giant to purchase 1,003 fastbacks, including two prototypes. Four "experimental" GT350 convertibles were also built for test purposes in anticipation of a 1967-1/2 convertible offering, bringing total production to 2,378 units for 1966. A small number of the 1966 models were fitted from the factory with Paxton superchargers, but not the No-Spin limited slip differential; with an option price of $670, the engine was rated at .