The engine and transmission and clutch are housed inside the same case… unless some serious modification has been done.
T-rex or a similar company makes a 3 wheel car that uses a Kawasaki ZX12 and ZX14 engine/trans.
The only bad thing about using a bike engine is keeping the weight down to abosolute minimum as the trans and clutch are made to power a motorcycle sized package.
Some other car builder took a hayabusa engine, machined their own block/case and made it a 8 cylinder - two head hayabusa.
