Value of 1969 GTO project car

[Dave Rifkin]

I have a neighbor who is selling his Verdoro Green 1969 GTO coupe. The front end sheetmetal is off of the car and, front what I am being told, the engine and transmission have been rebuilt.
The car needs work, the interior needs to be redone, the body needs rear wheel arches (at least) and needs to be painted.
The chrome is pitted; etc.

I am not a Pontiac guy and have no idea what the value of such a project car would be and would appreciate any help.
How do we tell if it's a real GTO?

The VIN is 242379G120258 if that helps.