Steering wheel on the left hand side........
I think as what was mentioned it comes down to the model. My personal view point is and the way I plan to build my cars (I currently only have a 2+2 but hope for a 240z in the future);
240z: Interior keep stock just freshen up, Period correct looking bucket seats are fine. Exterior is basic mods that can be easily reversed (no cutting the guards for flairs etc) just basically some nice wheels (simmons, watanabe, panasport etc) but no larger than 16", front lip and rear spoiler if you wish. Engine wise just some triple carbs, slightly bigger cam and a nice exhaust should do it.
260z: Well this is the race car base. Flairs, spoilers, larger wheels (17" is fine as its easier to get wider wheels for). Basically do what you wish with it but personally I would prefer to keep the engine swap within the L series and just mod the hell out of it.
260z 2+2: Do whatever you want