J. Lee, welcome to the forums! We own a 1974 20' Argosy mh and a 1984 310 mh.
I would be real surprised if you manage to find a newer replacement system that fits in the dash. You might be surprised at what you can do with the original one however. Most if not all of the parts are still available.
Check out the following thread for some information and pictures of some dash a/c work.
http://www.airforums.com/forums/f311...-ac-17683.html
Also here is the ACME website for a/c parts for recreational vehicles. You should be able to find what you need there.
Recreational Vehicles
Good luck and keep us posted!
By the way, for those of you keeping track, this is my 500th post
Brad