honda origninal equipment already has some of the best engine parts. anything that is ITR or CTR is good. Cams, valvesprings, retainers, valves, pistons, crank, intake manifold, exhaust manifold (header), etc. also companies like skunk2, toda, and jun make some very high quality parts like toda individual throttle bodies, or skunk2 racing camshafts. with an all-motor setup, almost all of the power is locked in the head. a good port on the head and the intake manifold, as well as a high quality valve job, and maybe some custom exhaust manifold work, like adjusting each individual primary will produce impressive results. all-motor is the most dependable way to go, but it all depends on how much you want to spend.