[Formulajones]

To answer your last sentence, as far as GM goes in general, I know Chevrolet had several versions of dual snorkel air cleaners, and even some single snorkel air cleaners that did not have any thermac valves.

The 70-72 LT-1 camaro and vette come to mind. Chevelles and Novas had a dual snorkel in early 70 for the L78 and LS-6. Even the single snorkel for the cowl induction setup on 69 camaro and 70 chevelle were without a Thermac valve. Started seeing thermac valves on cowl induction air cleaners in 71-72 Chevelles.

So wouldn't surprise me if other brands didn't have thermac valves on certain applications.