As 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[21]—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 and was very similar in appearance to the much later Pontiac Fiero.
It was claimed that the decision to abandon the two-seat design was in part due to the low sales experienced with 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 not available as a 1964½ model, but was first manufactured on August 17, 1964.
