1972 Duster Heater Control Unit - defrost question

Thanks for the referrals. I’ll check those sites out. Unfortunately there is no fender tag on the car. We only have the VIN and I haven’t come across any broadcast/build sheet that I often see people find behind their rear seats or somehow in the dash.

Hopefully between the sites you shared and the network here I’ll find a way to get the defrost working.
Thanks again