Introduced at the 1964 New York World’s Fair, Ford’s Mustang became an instant hit. By 1971, Mustang was wearing the original pony car’s third restyling. Sleeker than previous Mustangs, the ‘71 followed the classic American design formula of longer, lower, and wider. In 1969 and ’70, there were two “Boss” performance Mustangs. For 1971 they were replaced with a single Boss 351 model based on the racy SportsRoof body style. Under the twin-scooped Ram Air hood was a specially modified 330-horsepower 351-cubic-inch “Cleveland” small-block V-8. The golden age of muscle was quickly winding down, and production of the one-year-and-out Boss 351 totaled only 1806 units.