You can basically swap any SR or RB motors into any 240 model. I believe the 300zxs come with a V series motor in them and are a bitch to work on, so I'd stay away from them. I recently saw a really bad ass S12, might wanna go with that and be a little different.

EDIT: check this one out, already built and guy is looking for a FWD trade
fs: s13 240 sr20 with many mods, trades possible