A couple of quick things I notice. First the wheels and sidepipes are not original equipment. The ignition shielding is missing. The one thing that stands out the most in my point of view is, if you look closely at the first interior pic, the fourth overall, take a close look at the striker on the door jamb, see how it has blue paint on it, that tells me the car has been repainted, and they weren't too fussy about what they did and did not mask off. That might be indicitive of the quality of work done on this car. I personally would be leary of buying from a "Classic Car Dealer" as they usually by cars that need attention and do a minor resto to make them appealing. You would definately have to inspect the car in person.
I don't understand what they mean by this line in their ad "Several potential buyers have already been disappointed because they "snoozed". If you see one you like, call immediately or stop in and sign a contract." If they wanted the car why would they be disappointed if it is still for sale.
It appears to me that the only listings they have online are from dealers. To get private party sales you might have to suscribe. The only dealers I would consider buying from would be
www.corvettemike.com or Pro Team Classic Corvettes, here's one to look at,
http://www.proteam-corvette.com/cars/273W.htm
Here is a site you can check out,
www.vettehound.com
http://www.corvettetrader.com/
Another person from this board that might be able to help you in your search is Rich427. He owns a beautiful 69 Big Block and he might be able to steer you to places that specialize in C3's. Just PM him or start a thread paging him.