Mike,
I would say go for it, the r6 motor is heavier, but it has more tourque, double that of a banshee so it kinda weighs itself out and makes up for the weight. You add fuel injection in the mix, throw a pipe and power commander on it and your looking at 120hp easy on a 600cc. Ive ridden streetbikes for a while, you can beat the sh!t out of em and they are reliable as h3ll!...........Ive got a zx14 pushing 200 rwhp, If I EVER wreck it, hahaha just guess where the motor is going....good luck!