Mark do you know Tony Randazzo I believe they are in PA. ?
http://www.tonyrandazzo308.com/aboutme
on his site they show the 1969 Yenko Grossman ZL1 Camaro with Best Photo and Yenko on it
caption says " This was our Randy's Auto Body 427 Aluminum ZL 1 Camaro co-owned with Drivers BoB Grossman and Don Yenko we Finished First in GT at 12 Hrs. of Sebring Fla. 1969"