From the ad:
"We do not have the original engine / trans, but winning bidder will receive contact info of person with possession of complete original engine and trans (he is willing to sell)." Real world translation: He wants way more money for it than we're willing to spend.
"At one time, the vehicle was used as advertising and a drag car by a Chevrolet dealership. With a little digging, you could probably find some race history on the car." Real world translation: We looked and couldn't find anything to support this theory.
I hope those hokey 'Chevrolet' decals on the quarter panels are not the basis for the 'former advertising and drag car' theory. I remember when those were somewhat popular back in the 70's, but suffice it to say, I never had them on any car that I owned