I only have the Vintage Air heater/defrost and with the cowl vent I had to mount the heater on the firewall below the dash. Now I have to create a cover/fake firewall out of wood or fiberglass to hide the heater. I can imagine why anyone with an A/C unit would just weld up the cowl vent and mount it behind the dash as much as possible, but I wanted to keep the windshield hinged and the cowl vent.