For the 1973 and 1974 model years, Pontiac offered an extra option for the 2nd Gen Trans Am, the Super Duty 455ci V8. These cars had a unique hand-built engine from the factory. The SD-455 motor was based on the already produced 455ci and put out about 290hp/395lb-ft of torque. As the name implies, the engine wasn't just about performance; it was about durability. The engine had added material throughout the block and 4-bolt main to handle additional power and other modifications. 252 SDs were built in 1973. The SD could be ordered on the Formula model as well.