 The same year, Mercury shifted to a Ford-based chassis for its full-size model range, shedding 6 inches of wheelbase.Downsizing (in an effort to improve efficiency) was first phased in as Ford introduced the 1974 Ford Mustang II.Designed before the 1973 fuel crisis, the Mustang II was developed as a response for consumers who felt that the Mustang had grown too large through its various 1960s updates.