I remember seeing this newspaper clipping over at yenko.net about a year ago or so. It appeared in the Sunday, March 16, 1969 edition of The Palm Beach Post newspaper. (just over 50 years ago!)
According to the ad, both the Z/427 and the Stingray Aero Coupe could be seen at Sebring International Raceway which held the 12 Hours of Sebring on March 22, 1969