Drivetrains, well it depends on how far you want to go really. Try searching (I know the search facility can be awkward to use at the moment). Briefly:
A 280ZX flywheel will allow you to use a larger (240mm) clutch, but be careful to get the matching Pressure plate (6 or 9 hole) and release bearing collar.
A 'fairly' straightforward upgrade is to change the gearbox for a 200SX box. Some machining needed on your bellhousing and also modifications to your gearbox crossmember and prop (shortened).
The diff can be upgraded to a larger (but heavier) type (R200 200mm crown wheel instead of the R180) from a later 260 or 280ZX. Be careful of ratios.
280Zx driveshafts are better (CV joint type).
However if you want to be more radical look at the 'Introducing Gajin' Thread. He's used a R34 rearend I think.
My advice - keep the drivetrain as standard as poss but with just good condition parts until you've used the car a bit. Concentrate on the body - looks like you'll have a decent car to base any mods on. Are you keeping the sunroof (sorry if you've mentioned this already)? Whilst you are doing the body I would replace the roof - yes drastic I know but a more important mod than the transmission at the moment.