In the late sixties, Can-Am's rising popularity was showing no sign of let-up and, as a result, even Porsche was considering building a car to the essentially limitless Group 7 regulations. But where to begin? Considering the 1969 World Sports Car Championship had already been successfully wrapped up, and its new 917 had been recently introduced in time for the next year's new Group 5 regulations, it was decided that a modified 917 chassis would be entered for the remaining six races of the Can-Am season. Driven by Jo Siffert, a key player in Porsche's first victory in the International Championship for Makes, the 917 PA (standing for Porsche-Audi, the factory's American Entrant) was built in order to assess the chances of a full-factory effort the following year.
Development began in August, already five races into the Can-Am calendar. To avoid missing any more precious testing time, a single car was hastily built—chassis 028—and kept essentially identical to the 917 coupé mechanically, save for wider rims and lighter brakes. The chassis was converted into a Spyder to save weight (around 55 kg) and, without the time for wind tunnel testing, fitted with a tried-and-tested 908-style body. The reduction in weight meant larger fuel tanks could be fitted (180-litres as opposed to 140). The finished car weighed in at approximately 780 kg, though in comparison to the featherweight, purpose-built Can-Am prototypes, it was still pretty portly, mostly due to the hefty 4.5-litre flat twelve.