Go for a GSXR1000 swingarm. The GSXR600 swing arm isn't braced and I was told it was probably dangerous with the torque of a Busa...
...oh, and ignore those that tell you otherwise. If you love the Busa, ride the Busa. Probably much like me, you're not out there to win races. You're having fun, and to me, that's what matters. Besides, coming out of a corner on a 600 is boring after you've done it on a Busa!