Danny, if you want to go look at it just to go look at it, can you get the VIN and the trim tag info for me? Also the VIN on the engine pad. I can't see the last few numbers.
As for it being a real Z, the chances are doubtful. Yes, it has the 6k tach, but it appears to be a repop, and the gauges are 70's Nova. That and the small aftermarket tach at the lower part the dash tells me it's not working, so it probably didn't even come with the gauges. The steering wheel is hard to tell, but it may also be a repop. The horn button is for sure. The woodgrain radio bezel's from a Firechicken and the front and rear spoiler has more than likely been added. Check for the larger diameter torson rod in the trunk for that. Aftermarket shifter and cheapo traction bars as well.
Check for the 4 piston calipers and 12 bolt. He says it's got a 3.73 posi axle, but he didn't say if it's a 12 bolt or not. See what the VIN is on the transmission and if you can get at it, what the axle code and date are.
It's currently at 18k, which is about right for a car that's not really a Z. I wouldn't go too much over that unless he can prove what he says.