From the top of the text page 1 in the A/C section of the parts manual.
Note: All Parts Listed as Model "A" or "B" in the Part Name and Description Column Indicates used on Field Installed Units Only.
And wouldn't you know it, my parts manual was missing or had Illustration pages 24-1 and 24-2 out of order. So, here are the ones from MyMopar. These would represent factory installed A/C systems for A-Bodies. I don't believe there's a lot of difference un the mounts and pullies, but you never know. For instance, on illustration page 24-1, it doesn't show an idler roller and bracket, which mine clearly has, but the idler roller and bracket are shown as part of A/C Adapter Package (Model B), suggesting my A/C is a dealer add-on. My car clearly has the A/C firewall, however, so I'm pretty sure it's factory installed. I don't care really, it looks original and better still, it works well.
What are you trying to do? Find missing parts for an original A/C car? Or convert one built without to look original? Something else? Unless I had a show car, I think I'd just use aftermarket brackets and compressor. But, I'm a firm believer in one should do what he wants with his car. Too darn many people trying to tell others what to do.