In 1971, the Mach 1 started with a base engine of the 302ci based Windsor motor, with a 2 barrel carburetor, followed by four optional 351 Cleveland engines - the 2-V, 4-V (Venturi), the C.J. (Cobra Jet) and H.O. (High Output) BOSS 351. The H.O. was canceled after mid-year 1971, and shortly thereafter the low-compression 351 'Cobra Jet' became available.
At the top were two 429ci options, the CJ (Cobra Jet) & SCJ (Super Cobra Jet). Mach 1s, as well as all other Mustang models (except the BOSS 351) were available with the optional CJ and SCJ motors.
One of the most recognizable features of the '71-'73 Mustangs is the optional (standard on Boss 351) NACA (NASA) hood design with dual scoops. Though available as a visual, non-functional item, they could be made fully functional on models ordered with the Ram Air option, which included vacuum controlled 'flaps' inside each scoop, and a fiberglass under-hood 'plenum' that directed cool, outside air through a modified, rubber-ringed air filter housing and into the carburetor.