Trying to get the heater working

Thanks 67dart273! I have that '73 manual you spoke of, printed out the section you mentioned, and have it handy when I get started troubleshooting. And thanks for the tutorial on how to read that connector reference. I was confused on that. Should I have a vacuum reservoir on the inner fender? I don't. The PO hacked up so much stuff on this car I'm repeatedly finding things missing, incorrectly installed or just plain jury rigged.