Radical Extreme Sports Cars started building race cars powered by superbike engines back in 1996. They began using Suzuki engines and it looks like they have been fairly successful. Their latest creation, the SR8, goes a step farther. Instead of just dropping in a complete engine, they built a V8 by grafting two Hayabusa engines together. So far the figures are 372hp and the ability to rev to over 10,000rpm, which is not unusual in a motorcycle but quite a spin in a car. The SR8, depending on gearing can top 200mph. It seems we are seeing more of this kind of complex engineering lately and it may be the result of the wide availability of computer CAD/CAM software, enabling smaller shops to go places where only major firms used to go. The Motoczysz C1 comes to mind as another recent example of engine modifications by a small builder/designer. We may be seeing a lot more of this and I can't wait. This kind of inventive talent has always existed but now there are more opportunities for it to be realized.
See also Motorcycle engine powered cars