The pic of the engine pad is way too small to judge whether it's an authentic stamp - I sent a note to the seller requesting a larger image.
Pretty desirable car if it's what the seller is claiming. I see a POP from Ed Lee Chevrolet among the pics - would be nice to see a high resolution image of that, too.
Decent chunk of change for a car and I still don't understand why sellers don't take the time to provide all the right pictures for a prospective buyer to judge authenticity. The seller seems to know enough about '68 Z cars to understand what's important for a purchase....
Link to 1968 RS/Z Project Car auction
124378L332842