This topic has come up on facebook first generation firebirds https://www.facebook.com/groups/161277239570/user/100024674076842 and I am wondering if there was any more info on the subject other than what you found to this date of your post. I wondered many years ago why my early 68 11A did not have the bird glass and what I found out is similar to your conclusion is that they did not start to install the Bird glass until second to third week of Nov 67 Thanks in advance Chris.H.