I carry this from Dakota. Looking at this myself.
It works with a Vintage Air GenII Conditioning, NOT the Sure-Fit system for the 73-86 trucks. They have an oval version also.
The blower blows the hot air off the heater core into the vents for heat, it does all the air circulation in the system.
As for the AC, if you are just unhooking it the heater will still work, if you remove the box on the outside it won't be sealed so it won't work.