Air extractor grilles
A slightly obscure question for you.
On normal 65 and 66 mustangs there are air extractor grilles in the rear quarter panels which as the name describes, allow air our of the car. An early approach to through flow ventilation.
When theses are replaced by triangular Plexiglas panels either in Shelbys or for any other mod, how does air escape from the passenger cabin to the outside world?