In 1969, Ford developed a new engine for NASCAR. To meet NASCAR requirements, Ford needed to build a minimum of 500 vehicles equipped with the new engine for sale to the public. Thus, the birth of the 1969 Ford Mustang Boss 429 was ensured. Ford installed this hot new motor in the Mustang because the pony car represented the image they wanted in order to attract younger buyers. Multiple modifications were needed to make the engine fit into the Mustang’s engine bay, but in the end a company called Kar-Kraft custom-built 859 of the 400-horsepower Boss 429s.