The 1974 Pontiac Firebird and Trans Am Super Duties were the very last of the high-performance cars from the ’70s. The history of the Super Duty is legendary. The SD-455 changed the nature of the Trans Am entirely, helping to solidify the performance image that would carry the car through the later part of the decade. However, a little-known fact is that all the 455 Super Duty engines were literally hand-built race engines, as an off-assembly line operation. This was unheard of for a production vehicle, especially during the time of detuning and emissions regulations.