Well, I am a little farther along with the HRA install. I contacted Hot Rod Air several weeks ago and asked about buying the control panel since my kit came with the under column controls. I sent my standard controls to them and they sent me a kit to adapt the thumb wheels.The only other thing that I did was order a new lens to replace thenon-air lens. The interior will look stock even if the car is NCRS (Not Correctly Restored Stingray). I have enough polished aluminum and stainless steel under hood that it could never be looked at as correct and I don't care.

 

On the '73, the blower speed on high went thru a set of relay contacts, bypassing the resistors that control the lower three speeds. My experience was that the relay contacts would get burned to the point that they wouldn't pass any current.

The vacuum cans on the kick panels close the LH vent to outside air and open the RH vent while closing the outside air intake at the base of the windshield in the cowl when going to recirculate position.

Personally I wouldn't convert to R134a as it is less efficient in a R12 system. It requires a bigger condenser and evaporator, different O-rings, seals, hoses and gaskets, and higher pressures. The Corvette A/C was marginal at best and when you switch to R134a without changing the whole system, it will be even less efficient.

Good luck!