You can download a 73 wiring diagram on the MyMopar website. That's probably your best bet since I dont have access to my 73 at the moment. Sorry I'm not more help.
Thanks, I was unaware of that site. I'll check it out.
Here's my wiring diagram.
diagrams https://mymopar.com/wiring/
It appears there are 2-plugs in the four pictures
Looking at the diagrams it appears to be
1st 2 LT. Green, Black Green, DK Green - Heater Switch
2nd 2 DK Blue, Brown Yellow, Gray - Seat Belt Relay
Thank you Bullitt! I was wondering if driver side might be seat belts, but I can't find a mate under dash. The Passenger side, is there more connections than just the ones on face of heater box that you can see...maybe one on top?
On a non-A/C heater box the plug goes to the resistor on top if memory serves me.
Not sure on on the A/C model which is what you appear to have.
Wire is for the heater resistor.