Most Customs and Custom 500s were fitted either with a base inline six-cylinder engine or a small-block V8 engine (289 cid in the early years, up to 351 by the mid- to late-1970s), although the full range of V8 engines, up to the 425-horsepower 427 V8, and transmissions (from overdrive and 4-speed manual to SelectShift automatic) were available for law enforcement and performance-oriented customers who wanted the lightest car possible. As late as 1972, a powertrain combination of a six-cylinder engine and three-speed manual transmission was standard on the Custom and Custom 500 range; all V8-powered Customs had SelectShift made standard for the 1972 model year. Six cylinder engines and manual transmissions were dropped in 1973 due to the added weight of newly mandated 5 MPH numbers; all full-sized Fords from 1973 onward, including the Custom 500, had a V8 engine (351 cubic inches at its smallest) and SelectShift transmission standard.