Well, I finally found the replacement temperature sensor that monitors the heater core temperature. Bingo! That solved the heat problem. It took a while to realize it, since the heater core had already filled with hot water when I plugged the new one in. But this morning I got into the car, drove to work, saw the car was at operating temperature and everything was cool. In multiple ways.
Now I need to install the new A/C Compressor and get some R-12 shot in and everything will be copacetic.