Originally Posted by cletis
The door on the face doesn't dump heat into the cab. When the door is open it recirculates the cab air. It is connected to another door that closes the fresh air vent when the in cab door is open. Closing it draws in fresh air.

http://www.flickr.com/photos/advance-design_parts_co/8129312977/in/set-72157631868452754/
You are right Tim. I have one of each. The one with the extra cable and doors would allow you to bake bread inside the cab, or at least melt the shoes off the ole lady.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission