The Ford Mustang Boss 351 was produced only in 1971, and with a production run of just 1,806 models, it is a very rare car among Mustangs. Equipped with the 351 Cleveland V8 and producing a factory-rated 330 horsepower, the Boss 351 was capable of acceleration to 60 mph in 5.8 seconds and finishing the quarter mile in 13.8 seconds. The downside was that the Boss 351 had gained substantial weight thanks to the Mustang’s redesign, and wasn’t as fast as enthusiasts felt it should have been. As it turned out, 1971 was the final year for the Cobra Jet engines, and it would be a quarter century before another factory Mustang made 300 horsepower thanks to new emissions regulations that took effect in 1972.