If you are looking to add a roof A/C unit-
I added one in our ‘73 Argosy. We did it after going to a rally with 95 degree heat and no shade- felt like we were boiling in a soup can
Your trailer should be prewired for it as ours was- somebody more knowledgable than me on this forum should know the exact locations of the wires in the ceiling and where to cut the hole in the ceiling. Or look at the location on another trailer like yours. You will need to cut some curved supports (I did mine out of 2x4 pieces); to support the curve in the roof. They will slide between the inner and outer roof before bolting down the unit.
You will have to add another circuit breaker to your box. The other end of the A/C wiring should be inside the wall behind your circuit breaker box. You will need to unscrew your box from the wall; cut a hole in the wall just big enough for your hand (that will be covered up when you put the box back), reach in the hole and pull your wires out.
Definitely worth the time and effort- you will need a freind to help you lift the unit onto the roof; but other than that, pretty easy.
Have fun,
Shawn