The Boss 351 produced 330 horsepower, while both 429 engines produced 370 horsepower. On the exterior, the famous Mustang corral returned. A new wide chrome strip on the edge of the front fenders and hood was borrowed from the 1969 Shelby's. The long hood now turned up at the windshield to cover the hidden wipers. Large, bold, triple lens tail lights appeared on the rear of the new Mustang. Flush mounted door handles replaced the earlier surface mounted units.
The interior featured standard high-back buckets, a mini console, and an all new instrumentation layout. Power windows were offered for the first time. The Mach 1 continued to be offered for '71. It was available with any of the V8 Engines. A special honeycomb grille and color keyed front bumper were unique to the Mach 1 model. The chrome hood and fender moldings were replaced with color keyed trim. "Mach 1" decals were placed on the fenders and deck lid and a special black or argent lower body side paint was used.
New for 1971 was the Boss 351 which replaced the Boss 302 and Boss 429. The Boss 351 featured a special 330 horsepower 351-4V Cleveland engine. The Boss 351 featured a blacked out NASA scooped hood with twist type locks and special body side stripes. The Boss 351 included a competition suspension with staggered rear shocks, a four speed transmission with a Hurst shifter, power front disc brakes, dual exhaust, and 3.91:1 traction lock rear end. There were a total of 151,484 Mustangs built in 1971.
Very few 1971 Shelby Mustangs were built.