N47 on dished pistons with a T3/4 turbo .50 in, .63 exhaust, that's what I'm running now.
since I've never seen a P90 head, this is my next best thing.. peanut shaped combustion chamber to help with swirl, dished pistons to drop the compression ration, and once I un-shrouds the valves, it should add a few more cc to the head.
I'm going to build a L28 with a N47 head (reason I'm after a second head), maybe put the larger valves in, haven't decided yet, as it all comes down to cost
Nigel