If this is the engine I think it is, it is loosely based on the Yamaha R1. The basically started with a pair of heads built blocks to use them, then made their heads following the originals basic design (but not identical or even with interchangeable parts).It is a bike V8, basically two Bike engines bolted together in a V.
Well, it is more like only the heads are from a bike and everything else like block, crankshaft, cylinders and gearbox are custom made. Weight about 73kg or so, without Gearbox though. I guess it weights less than a 50hp 1 litre car motor then.