full ex, pc & you'll get the most from the redoing the heads-porting it, sinkin the valves into the head, etc., without losing reliability. aggressive cams, bigger valves, pistons, bump up the c.r. alil, and match all the parts to each other should get you where you wana be, but reliability can suffer .
150 at the wheel....why not a 1000rr? way cheaper, and more reliable than a hot rodded 51.
just saying-maybe you're racing it, idk