the so-called "1964 1/2" mustang was designed by joe oros and dave ash of ford's mercury division, was based on another ford car, the falcon and was proposed by ford's president, lee iacocca. the falcon was not expensive to build and that helped iacocca get the mustang the approval it needed to be built. the people who ran the ford company did not want to take a chance on a car like that because they lost a lot of money on another car, the edsel, just a few years back. it set sales records and became one of the best selling cars of all time. it would remain mostly the same until 1966. so popular was the mustang that three ford assembly plants worked to build it. not only was the mustang built in dearborn, but in metuchen, new jersey and san jose, california as well.