Everyone will have a differing opinion. My story, for what it's worth:
I bought a fairly well sorted 2-seater 260Z which had received a very professional V8 conversion - warm 350sbc, disk brake upgrade, coilovers, etc. Solid, rust free, fantastic condition underneath, great paint, excellent trim but in need of cosmetic work. Great base from which to continue the development. It had a TH350 auto which I knew had to go, so it has now had a transplant - a 6-speed Tremec T56 from a Clubsport R8. (big job) Then all the instruments were replaced with Autometer Pro-Comps, and so on it goes. Lots more in the pipeline yet.
That's one way to go. Tons of grunt - a real muscle car and far from subtle.
My next project, though will be a 240Z with the classic period mods - worked L24, triple webers, 5-speed, 16" Watanabes, etc - Wangan Midnight style, if you will. Light, nimble, yet with a sting.
Why the 240Z? Because it was the first. It has that simple, charming, almost naïve quality that comes from the first model, the product of years of design work which produced the car that burst onto the scene and captured the imagination. The design that the engineers had spent years sweating over and was yet still far from perfection. It has endearing faults, yet represents the first and purest form of the beast.
Later beefed up and 'improved', often just for the sake of change, the 260Z was a second iteration. Nothing fresh - the impact had aleady been made. Subtle body strengthening, 'revised' dash layout, anti-pollution gear creeping onto the engine, but none of the brash 'new kid on the block' about it . Just a solid lookalike. Then the gradual slide into middle age oblivion, overweight and sluggish 280Z, then the awful 280ZX, both of which are to be avoided at all cost.
So for me two different approaches, but both far from stock. I went through a phase years ago of fastidious pursuit of originality, down to infinite details like correct underbonnet decals, nothing repro, everything nos and EXACTLY as it was from the factory, etc, but these days, nah - but I do respect those who are still on that journey.
I'd say: be prepared to pay for a well sorted example, not a 'Hugo' rust bucket, a 240Z or a 260Z 2-seater, if you can find one, that doesn't need too much work and go from there.
But ultimately it's all about what YOU want.
