I can say that on the old ones, hot air comes into the center console from two places and having neutral or negative pressure in the cab from having windshields front and back makes it flow in much faster and easier. The air from up front is from the radiator blasting back and down the firewall into the open channel. It also rolls up and over that same plastics and dumps under the dash. That too can be sealed. I did both with chunks and strips of memory foam. The rear is open to the engine bay behind the plastics and is tougher to seal-off but can be done with some plastics fabrication work....maybe some foam too but be aware there is an exhaust pipe there that can burn things too close.