My 67 had them also. There was a slider on the inside of the pillar that the rear passengers could use to open the vent in the louvers. I don't imagine it would be to tough for some company to make something like this up. You'd have to remove the window glass obviously to install it, so it would be pretty permanent. You'd just have to make sure it was sealed up real good. Hell, Shelby did the opposite on the 66, removing the louver and putting in window glass, you'd just be doing the opposite. I think this would be light years better looking than the ones that just sit over the window glass, and plus functional.