The Mustang was successful because it had an attractive design and an inexpensive starting price, and it could be optioned out pretty much however you wanted it. Let's say you wanted the fastest Mustang money could buy in 1964, in an effort to impress the young thing sitting next to you at the soda fountain. The K-code engine was able to create so much power as Ford designed it for the larger Fairlane with higher compression, different cylinder heads, and freer-flowing exhaust manifolds.