There was a heater delete option available after 1968 as a dealer installed pkg. I saw a A12 RR that had one.

A car with heater delete will have special vent boxes under the dash instead of the regular heater box. I have a '67 Belvedere II, heater delete (and radio option not selected thumbs). I also have a '68 V200, no radio
I love stripper Mopars.