I posted this comment and then read zKars comment above, were saying the same thing I guess.
Although there is a strong market for early numbers matching 1970 Z's, in order to get the $40,000-60,000 prices you would have to put at least that much into the car. If you do the work yourself and you are good at it you can break even or make a bit but your labour has to be free. Your car being made in May of /70 is a good example of a series 1 car but it's not really considered early. The most money is going for cars that are under the 00500 serial number. The outside sheet metal looks solid with no serious dents or dings and looks like a good candidate for dumping lots of money into I'm serious though.
I just sold my 03/70 Z on ebay in the spring, got $19,400 for it. I spent 4 yrs restoring myself, I got my cash outlay back and maybe 2 cents an hour for my labour, but my labour is free and I had a great time working on it.
On this forum the love of all things Z is almost spiritual, deity like. When someone comes on asking what their great buy is worth you can practically hear the teeth grinding (mostly because we didn't get to buy it before you) So don't be offended if we don't fawn over it. The best thing I can see about your car is that it doesn't look like it has been messed with too much, the engine bay although in rough shape looks original, the car looks like it may have had a respray in the past but quite original.
Good luck with it, be nice to it.
Chris