Underneath, the 1969 MACH 1 Mustang offered a 250-horsepower 351 Windsor V-8 or a 335-hp 428 Cobra-Jet mill. Mach 1 and its stablemate, the Boss 302 Mustang, reenergized the fastback, tripling sales of the body style in 1969. The much smaller Mustang II model, introduced in 1974 as a response to the nation’s “energy crisis,” was the weaker sibling to its older muscle car brothers. The 1974 Mach 1 featured a 2.8-liter V-6 with dual exhaust while the other Mustangs of the period carried 2.3-liter I-4s as the base engine.