This is a shot of part of the modified A/C unit showing how I split it so that cold and hot air go separate paths. I added a micro switch to operate the vacumm switch which operates a vacuum heater tap under the car, splitting heat from the front and rear heaters. This thing is long so needs a heater under the reat seat, and an A/C unit behind the rear seat which is ducted up along the roof lining above the doors for the rear compartment. I then built a duct under the plenum to take the cold air to the vents in the dash. I added two demister ducts under the windshield, note the safety shoes for welding.