I like that car, needs better wheels but looks good. Would be nice to see the condition in the flesh. Advantage here is that it’s in the UK and you can view it, bodyshell condition is primary for a Z, forget interior colour and if it’s a manual..
Find yourself an S14 box in good condition (400-500 tops) and a manual pedal box for probably around 100. Chuck another 400 in for clutch flywheel and other small parts... probably get it all fitted for 500-1k depending where in the country you are and who does it.
Interior, stick with the red, it’s a selling point imo, just freshen it up with any parts missing and some new bits as needed when you start getting into it.