According to the story I've heard, Shell asked for three cars, they got four GT40s from Ford.
I'm not sure about Bernie's story about the plates.
Even getting the cars to the track was an adventure, Reeve remembers. "The GT40s technically had to be registered for the road to get them into Italy, but we had a selection of plates with us, and my John Coombes-prepared Jaguar Mk 2 was packed with props,"
I've seen a photo (from John Horsman) of the four GT40s parked in the Alps, and the four cars have number plates (letters on the grill) that match the plates of the four cars as listed in the Ronnie Spain book. That suggests the GT40s had been registered before they left the UK.