F70 x 14 fiberglass belted RWL tires [option PL4] became available as a 69 Camaro option as of the 1 April 1969 ordering info. Considering order lead time it is unlikely a Camaro built prior to 1 May 1969 could have had them as original equipment. Most OE tires were poor in those days so it was not at all unusual to immediately upgrade tires while the car was new. The only way to know for sure is original paperwork.
Incidentally the only documented '69 Camaro known to have been built with PL4 tires is a COPO and it has Firestones.
I wish I still had my spare - My 06(C) 69SS originally came with the polyglas tires. I had the spare for many years until a friend needed a spare... I never got it or the rally wheel back
