1964 Dodge Dart 270 Slant Six Restoration

We will give it a try...may have to get a manual out. Not sure what type of refrigerant,is there a tag on the compressor or radiator support?how old is the a/c unit?
The a/c unit has a metal tag on it that says something like “for parts, visit one of our retail stores or mail catalogue - Sears Roebuck & Co” and then an item number. I’m guessing mid-70’s. I’ll do some research and see if i can procure a manual