Bad feeling this is gona get fucked real quick. Prove me wrong.
But If your really looking for power than the cross flow isnt a powerhouse by any means, like magnum said if you want to stick with the crossflow get a new cam (kent cams 234 or 244 or give kelford a call up and see what they can do) Bike carbs go for it or dual side draughts, up the compression using 1300 x flow pistons, port and polish, 2" exhaust and youll be good for 110-120hp. And last but not least start setting your budget and think about what you want from it, G-rolla, daily or thrash it to fuck.