I can't speak for Camaros specifically but the Goodyear Polyglas tire was available on a number of 1969 model autos both as standard and optional. I worked for Goodyear for a few years during this time period and seemed to recall these tires being available before 1970 as both 78 series as well as the "wide footprint" 70 series which appeared on the higher performance cars.
Scroll down to the notation under 1968 from the Goodyear website.....
http://www.goodyear.com/corporate/hi...ry_byyear.html