I have an 81 that had a/c but that has all been removed. all i have are the controls. when lookin for parts i am ask dealer or factory installed? does it matter and how do i find out which one i have?

 

do the controls look original. I mean the heater switch slides over to the A/C mode. If so, more than likely its factory installed. Not sure but read up on how to decode the VIN number. It may have option codes in there but prob not.