Lee Iacocca's assistant general manager and chief engineer, Donald N. Frey was the head engineer for the T-5 project—supervising the overall development of the car in a record 18 months[20]—while Iacocca himself championed the project as Ford Division general manager. The T-5 prototype was a two-seat, mid-mounted engine roadster. This vehicle employed the German Ford Taunus V4 engine.
It was claimed that the decision to abandon the two-seat design was in part due to the low sales of the 2-seat 1955 Thunderbird. To broaden market appeal it was later remodeled as a four-seat car (with full space for the front bucket seats, as originally planned, and a rear bench seat with significantly less space than was common at the time). A "Fastback 2+2" model traded the conventional trunk space for increased interior volume as well as giving exterior lines similar to those of the second series of the Corvette Sting Ray and European sports cars such as the Jaguar E-Type. The "Fastback 2+2" was first manufactured on August 17, 1964.
A 1965 Mustang Fastback. 1965 was the first year the Mustang was available with a Fastback model and a 289 cu in (4.7 L) engine
Favorable publicity articles appeared in 2,600 newspapers the next morning, the day the car was "officially" revealed.[21][22] A Mustang also appeared in the James Bond film Goldfinger in September 1964.[23]