My heater leaked badly so had to pull it. I'm not going to use it again. It was the round kind that recirulated the air. I want to install a heater that pulls in air from outside. No it doesn't have to look stock. I have a small heater with core that works good but uses inside air. In order to make it use outside air I could Fab a small piece of sheet metal an duct it outside. How big does the air intake have to be to work good. I'm also concidering adding another fan to the system. Any ideas would be helpful. Thanks