It may be dealer installed AC. I had a 71 Challenger that had factory AC, was built in the LA plant, and lived the majority of its life in CA. It did not have a vent on drivers side, and the lower cowl never was cut and flanged. We have a 69 Dart GT conv that is a factory AC car, and has no vent on the drivers side and the lower cowl was never cut. I'm not sure when they started that though? My 65 Barracuda is a factory AC car, and it has a factory fresh air vent on the drivers side.