If you’re searching for the ultimate Pontiac bruiser, you could do worse than choose the mighty Firebird Trans Am SD-455. SD stands for “Super Duty,” and in Pontiac-speak that means the 7.5-liter V8 has been prepped for competition work: forged internals, high-flow heads, and a hot cam made it the most powerful American engine offered by a manufacturer in 1973. Way underrated by Pontiac, the big motor made around 371 horsepower and an astonishing 480 ft-lbs. of torque. Just so you wouldn’t be confused about which Firebird you were looking at, Pontiac also loaded the SD-455 up with visual enhancements—the hood bulge shouted “SD-455” to onlookers, and the rear spoiler was likewise emblazoned with large “TRANS AM” script. Interestingly, 1973 was the first year for the soon-to-be-legendary Firebird hood decal, known affectionately as the “Screaming Chicken.” While the decals didn’t make the SD-455 go any faster, it didn’t need any help in that department, as it was capable of 14.5 second quarter-miles dead stock. The SD-455 package was very expensive, which means that not many were produced, making Forza one of the best places to experience this rare bird.