Autoxcuda, there have been numerous other detailed photos on the internet of the finals at the venue shown in 1967. They have clearly shown the venue and the Barracudas without any round side marker lights.
The 1966 finals was at Detroit. I do not know the car model used.
The 1968 finals was at Indy Raceway with notchback and fastback Barracudas that all had round side marker lights.
The 1969 finals was at Indy Raceway with Road Runners. Every picture that I've seen has shown all hardtops.
The 1970 finals was at Indy Raceway with Dusters.
I don't know where you came up with December 1967. Snow and cold everywhere, none on the pictures.
I misread what you said Detroit 6/67
