I was at the Philadelphia Auto Show, and while they did not have the Carerra GT on display, at the VW corner there was a cutaway of a W8 on display. I noticed one thing about it: it was the perfect length for a 914 engine bay. I didn't measure it, but it looks like it would just drop right in with almost no modification (except for radiators, etc.)
So... with 270 bhp out of the box, which is probably easily boosted, has anyone tried a W8, or Phaeton W12 swap? You could keep it a VW/Porsche, and still kick the 911's asses all over the track. A Bentley W12 or Bugatti W16 would probably be overkill, though...