After having retired from F1 at the end of the 1962 season, Porsche focused again on sportscar racing. The 904 debuted late in 1963, for the 1964 racing season, as a successor to the 718, which had been introduced in 1957. Porsche designed the GTS variant to compete in the FIA-GT class at various international racing events. The street-legal version debuted in 1964 in order to comply with Group 3 Appendix J homologation regulations requiring a certain number of road-going variants be sold by the factory. Porsche produced 106 904s at four or five a day with a list price of US$7245 (FOB Stuttgart). Orders far exceeded the one hundred car requirement to satisfy homologation rules and more cars could readily have been sold. The 904 marked the beginning of a series of sportscars that culminated in the mighty 917.