Pontiac Trans Am 455
The 1971 Firebirds and Trans Ams were practically identical to the 1970 models. They still represent one of the best muscle cars in the rapidly changing market. 1971 proved to be the last true muscle car model year in which buyers could get high-powered and legendary engines. Just a year after in 1972, horsepower ratings started to go down (via Motor Trend).

But the biggest news for the Firebird/Trans Am lineup was the introduction of the mighty 455 V8. The biggest engine ever to appear in this model. The 455 V8 had 335 HP, but muscle car enthusiasts argue that the number was underrated and conservative since even with higher compression in the Trans Am H.O. version, that 455 V8 had the exact horsepower figure. The actual output was closer to 400 HP with corresponding performance and top speed.