Jeff, I was at one time looking for an '82/83 ZX NA, because of it being Z-like (same drive train, sort of) and having a T-top to satisfy my partner's yearning for a convertible. I traveled quite a bit looking at these cars and gave up. The reason was that all the "rust free" cars I went to see had penetrating rust bubbles in difficult places (e.g. the leading edge of the roof, and the non-removable vent cowl area). One fellow even had me drive across 2 states to have me see his rust heap that was barely running ("runs great"). When I pointed to the very obvious rust bubbles peppering the roof, he shrugged and said, "yeah, rust bubbles." PISSED ME OFF -- because I asked him several times whether there were any rust bubbles in that very area, and he repeatedly insisted, "no." So there's some advantage to local, IMO. You can run yourself ragged looking for a good Z in far-off lands, only to come away empty handed or buying something less than you expected expect. Of course if you enjoy the thrill of the hunt, then none of this applies. ;-)
As far as market value for a 280Z... Well, I've looked at completed auctions (at least the ones that actually sold) on eBay, and I'm shocked at some of what I see. I see a lot of bodies that need as much work as mine, with ratty interiors and "runs good" engines selling in the $6k range, and my car is much better than that. That's where I have to admit I'm out of touch, hence my question here. My "feeling" is that $6200 would be fair in a flat market, but I'm seeing signs the market hasn't been flat.