In the current era of Grand Prix and sports car racing, there is virtually no such thing as a new model racing car from a team or manufacturer and, at least on the surface, the 2003 F1 Ferrari looks like the 2002, which looks like the 2001, etc. However, it was not always thus.
In the very short period of five years, from the summer of 1963 until late in 1968, Porsche produced new model after new model in rapid succession, evolving the milestone 904 in the summer of 1963 into the world conquering 917 in what now seems like the blink of an eye.
