ALthough I think those suzuki motors are pretty neat Ill put this out there.
once you add an alternator, a primary drive, a clutch and a 6 speed gearbox, that suzuki motor wont be any more compact than a Yamaha RZ/Banshee motor.
You can easily and cheaply get that much power from a banshee/RZ motor, people have added EFI to them in the past with kits you purchase over the internet, and they fit into MX bike frames as done by a few people already.
In saying all of this, I am still trying to convince Neil to merge a sled motor with a 600 sport bike gearbox so that it will drop straight in, because I do see the benefits of a modern/reliable big bore EFI 2T.