Retro fitting an AC setup.

You didn't tell us what engine it has. Most (all?) w/ the floor shifter had a 273, which is easier since same as later small blocks. Your engine bay is 1" narrower, but shouldn't matter. If a slant, there is a long post on options. The factory AC climate box isn't a good choice since those cars had a different firewall. An after-market behind-dash unit seems better.
It is a /6 and Dartman has given me a lot of info and pictures on what to expect on the process of going for the factory install. Mostly, I'm hunting that all illusive dash bezel. Without it, the whole thing is a bust for me. He has introduced me to a second option which I'm interested in as well.