i am about to build the l28 for my 240z and am looking for around 200hp N/A.

Which head would be the best to use i currently have a p90.

also should i keep the hitachi su's or use 28zx fuel injection?

once you know bore size and desired compression ratio you want I.E. head volume and piston setup domed, flat or dished.once that's done, Its all about how much air and fuel you can cram in there. Cam and air fuel delivery ect.. If your talking about the flat tops then yes ditch em. Use a p90 or N42 it really doesn't make a huge difference. Hell a ported E88 would do it. But you eventually come to Carb Vs. F.I. I prefer carbs "less wiring and hassle" however each has it's perks and draw backs. throttle response and fuel economy and so on. I personally would run some flat tops with a N42 block decked and head shaved and shimmed and ported topped with a cam with a long duration. Should be good enough... I think