1200 is no question best bang for the $$ on these bikes.
Yep at one point I even saw a kit to do up to 1400cc without modifying the case, and then was going to add a 6speed Andrews trans too. I figured I would kill myself. I have seen these 1200s punched out to the 1350-1400 range and are pretty reliable, but big $$$ to. I even recall a few kits going larger yet. I love my Harleys, but I think for the person that rides 120mph+ a lot, not me any more. Get a Buell or another import or maybe a new Vrod.
Guess I am getting old. I still like the acceleration stuff and major ability to pass folks from 0-90 though.