In its refined form, the 1965 GT350’s powerplant was capable of producing 306 horsepower at 6,000 rpm, propelling the Mustang to top speeds of 138 mph and a 0-to-60 mph time of 6.6 seconds. This power was directed downstream by a Borg-Warner T-10 four-speed gearbox. In total, 521 production model Shelby GT350 Mustangs were built prior to August of 1965, when manufacturing efforts for the 1966 GT350 began.