the banshee chassis just isn't tall enough to fit the engine.. You'll have to cut the top rails for the motor to fit.. also.. when doing a street bike swap you'll loose 20-30% of the bike engines rated power by putting it into a quad.. There was a big write up about it on another site. If you dig around over on planet sand you'll find it.
You'll find that you'll get beat my much smaller bikes in a drag race. Ask loco, he's done the swap.
I'm not saying not to do it.. just giving you some idea on what to expect.