I haven't taken too much time to search various archives, but I remember reading - well over a year ago - a fascinating thread about AC units....
It referred to a guy who didn't want a big AC compressor marring the look of his vintage Airstream's streamlined silhouette, so he installed a small unit underneath his front dinette, (or gaucho, or whatever.) It was somehow vented to the outside, perhaps through a hole in the belly pan and I thought it'd be really sleek to have the cold air pumped through flexable ducting between the inner and outer skin, and come out flush mounted vents in the ceiling. (I'm guessing it would be less tricky than putting AC into a hundred year old house with plaster and lathe walls and ceilings, which people do all the time.)
I don't know remember any further details, but since we're doing a total gut rehab on our GT, I think this is an idea we'll definitely want to persue. It's possible this was at the Tom Patterson archives, so maybe I'll look through those as well. Let me know if you recognize the topic of which I speak!