Chip, the A/C on my car started with a Vintage Air mini system. The components are dismantled because the complete unit is difficult to install intact. When I dismantled the unit, I kept the vacuum servos and the flapper valve units. I used one of these to control my fresh air vent which has two hoses coming from each of the small NACA ducts on the nose. (This was the section that went to the defrost on the original unit.) You can buy these vacuum servos from Vintage Air. I am not sure about the flappers, but they are just a piece of thin metal tacked onto a thin rod with a bell crank on one end that the servo hooks to. The metal plate has a piece of foam glued on as a seal. Oh yeah, Vintage Air also has these little solenoid valves that control the vacuum to the servos. So I have a toggle switch on my console that turns on/off fresh air. Another turns heat on or off. Unfortunately, the vacuum valve for the heat is either on or off. I suppose I will use fresh air to regulate temp.