Rolls V8 Motorcycles
uses a Rover V8 in a TIG welded custom frame with a
Suzuki front end, there are bikes in both longitudinal and transverse
configurations
The bikes are single speed and use an electric/hydraulic clutch setup but it
looks like he is working on a 2 speed.
Rolls V8
Motorcycles also offers a
primary drive for Rover V8s in the transverse configuration in case you want to
roll your own.