69 Camaro Cowl induction?

[Ls6 Ragtop]

I was always under the impression that early 69's were flat bottom based, and that the switch over to the indented groove base was sometime around August of 69 during the initial 70 build. This base I don't think is correct for any 69 or 70 model as the breather elbow is the 2nd design style part # 6485891 vs the 69-70 part # 6485235 which uses a different elbow.