1969 Watkins Glen Trans-Am Poster Pic Below.
Though the poster shows a '68 Shelby Trans-Am Mustang, the date coincides with the 1969 race. In addition, the text talks of the 1969 season.
"Roger Penske Sunoco Camaros for Mark Donohue and Ronnie Bucknum... Shelby Mustangs for Peter Revson and Horst Kwech... Bud Moore Mustangs for Parnelli Jones and George Follmer... AMC Javelins for John Martin and Ron Grable... a Pontiac Firebird for Jerry Titus"
Sorry about the formatting. It's the best I could do with shooting a framed poster mounted fairly high up in my garage.