My one relative who was once a GM Canada exec said he believes FGFs in Canada were assembled in Oshawa, Ontario. As for St. Therese, I have it that assembly started there well after '69, though FGF body parts are said to have come from there. Again, all of this is based on recollections from those in my GM family here.
By the way, my VIN says my '68 rolled off the line in Lordstown...one of many thousands.
Mark
68 Firebird 350 auto (sold) 70 Trans Am RAIII 400 4-speed (sold) 2011 Challenger SRT8 IE392 6-speed (sold) 2017 Challenger Hellcat 1966 Dodge Coronet 440