I ride a Buell X1 that is pretty well modified, and let's face it the inline fours are hard to keep with. I agree with enough cash anything is possible, but, BIG BUT. Harley's are not designed for speed.
BTW you are probably wondering why this guy with the Buell is lurking around. Well hopefully by the end of this season I, in my mind, will feel I am ready for the Busa.