GTO drivers to compete against other 250 GTOs. The 250 GTO was one of the last front-engined cars to remain competitive at the top level of sports car racing. The 250 GTO gradually passed into obsolescence following the 1964 season. Scuderia Ferrari withdrew the 250 GTO from its racing activity by 1965, leaving only a few independent teams and private owners to campaign it in endurance races, rallies and hillclimbs. By 1967, the 250 GTO was almost entirely absent from international racing, with only a few rally and hillclimb results during that year. Prior to the development of the 250 GTO collector market and associated vintage racing and show events, some of the surviving 250 GTOs were used in regional races, while others were used as road cars. Homologation FIA regulations in 1962 required at least one hundred examples of a car to be built in order for it to be homologated for Group 3 Grand Touring Car racing. Ferrari built only 36 250 GTOs (33 of the 1962-design Series I cars and three 1964-design Series II cars, with revised bodywork). The additional three "330 GTO" cars with the four-litre 330 engine —recognizable by the large hump on the bonnet— are sometimes included in the overall production number, bringing the total to 39. It became a popular myth that when FIA inspectors showed up to confirm that 100 examples had been built, Enzo Ferrari shuffled the same cars between different locations, thus giving the impression that the full complement of 100 cars was present. In reality, no deception was required, as the production of the 250 GTO was covered by the homologation of the earlier 250 GT Berlinetta SWB model. These homologation papers were issued in 1960, but extensions were applied for and accepted multiple times between 1961 to 1964, allowing Ferrari to add modifications not covered under the original specification, including changes to the engine, transmission, and suspension. Additionally, since more than 100 bodies had been built according to the earlier 250 GT SWB specification, FIA regulations allowed a new body to be designed, leading to the development of the new 250 GTO body style. This method of homologation was not unique to Ferrari, as similar methods were used to homologate the Aston Martin DB4 GT Zagato and the Jaguar E-Type Lightweight. Collectibility While the GTO is now arguably the most valuable collector car in the world, it was