[Martyn L. Schorr]

Dave:
If I remember correctly, the money-back performance warranty was offered first in 1968 on Phase III 427 Camaros and then extended to Nova and Chevelle models. I don't recall the Phase III Corvette being included unless it was a track-prepared car.
I drove and photographed the Corvette in the article that Joe Oldham wrote and it was a pretty normal street model.
Marty