War II, advanced aircraft piston engine development had provided a great deal of available data, and NASCAR was formed just as some of the improved technology was about to become available in production cars. Until the advent of the Trans-Am Series in 1967, NASCAR homologation cars were the closest thing that the public could buy that was actually very similar to the cars that were winning national races. The 1949 Oldsmobile Rocket V-8 with a displacement of is widely recognized as the first postwar modern overhead valve (OHV) engine to become available to the public. The Oldsmobile was an immediate success in 1949 and 1950, and all the automobile manufacturers could not help noticing the higher sales of the Oldsmobile 88 to the buying public. The motto of the day became "win on Sunday, sell on Monday." However, in spite of the fact that several competing engines were more advanced, the aerodynamic and low-slung Hudson Hornet managed to win in 1951, 1952, and 1953 with a inline six-cylinder that used an old-style flathead engine, proving there was more to winning than just a more powerful engine. At the time, it typically took three years for a new design of car body or engine to end up in production and be available for NASCAR racing. Most cars sold to the public did not have a wide variety of engine choices, and the majority of the buying public at the time was not interested in the large displacement special edition engine options that would soon become popular. However, the end of the Korean War in 1953 started an economic boom, and then car buyers immediately began demanding more powerful engines. Also in 1953, NASCAR recommended that the drivers add roll bars, but did not require them. In 1955, Chrysler produced the C-300 with its Chrysler FirePower engine OHV engine, which easily won in 1955 and 1956. In 1957, several notable events happened. The Automobile Manufacturers Association banned manufacturers from using race wins in their advertising and giving direct support to race teams, as they felt it led to reckless street racing. This forced manufacturers to become creative in producing race parts to help racers win. Race teams were often caught trying to use factory produced racing parts that were not really available to the public, though many parts passed muster by being labeled as heavy-duty "police" parts. Car manufacturers wanted to appear