After the first-generation 911 had been in production for over two decades, Porsche began development of its successor, the 964, in the 1980s. And one of its ideas was to use a V8 engine. So it took a 964, borrowed a V8 from Audi, gave it the rear bodywork from a 959 and dubbed it the 965.
The idea was to create a more affordable successor to the 959 that included its advanced all-wheel drive system and active suspension. The Audi V8 would have been replaced with one of Porsche's own design – possibly based on the it had built for Indy racing – but Dr. Ulrich Bez (who was then head of Porsche R&D long before taking the reins at Aston Martin) ultimately killed the project.
That doesn't mean that Porsche has forgotten about the project altogether, as it has just brought one of the prototypes out of its archives to feature in the video below. Enjoy.