if you're looking at modding the car, go with a 95 m3 for the OBDI setup. (96+ is OBDII - not as mod friendly). otherwise, it'll be more difficult (and expensive) to see gains from the bimmer. if you're looking for a good stock car, i'd take the m3 over the 300z. switch out the plastic water impeller and your engine will run forever with proper care.