Boost the D. There are plenty of guys making a lot of power on D series motors. A set of Vitara pistons and tuner toys rods make for a cheap built motor that could handle 350 whp reliably. If you just want a low boost setup, a small snail will wake that engine up tremendously. Check out some of the setups here, on honda-tech, hmt, etc. This guy has a good build going. He is the guy to ask about this kind of thing.