[A/S] New member/AC question

["coptopusmc" <coptop8@xxxxxxx>]

I am brand new to this list, so hope I am proper with my first post.
I have a 1972 Land Yacht. I bought it after my house was flooded in 
1999 and lived in it for 15 months while my house was being rebuilt.
It has been sitting in the back yard neglegted and used for storage for 
almost 5 years. I am now starting to restore it.
My first question is this. I need to install a new Air Conditioning 
unit and would like some ideas on which brand is best and easiest to 
retrofit into an older Airstream. What is the best BTU's to cool a 31' 
trailer?
TIA:
Steve L