Originals were the Lampredi twin cam (2.1 litre I think) with a 16v head and Volumex Supercharger. But bigger than the one you find on the Fiat/Lancias of the era. Engine was also upright and not canted over, inline and not transverse. I also think it used a ZF box.

Micks car appears to use the right engine, smaller supercharger but I'm not sure of the gearbox he's using. Audi?

Guy