I just installed a second a/c on my sabre.
Now with that said my friend and I was able to set a/c of the tailgate of my truck to the roof.
My camper was only 30 amp so it was not prewired so I ran a new service for the second a/c.
My camper also had the blocking already installed for an a/c.
Your 50 amp should be prewired and have the blocking.
Just pull down the inner vent trim ring and you should see the blocking for and aft.
If you feel around you should also see find the wiring.
I went with the non ducted unit vs the ducted model and the install was straight forward and easy.
Tonight I had both a/c ' s running and it cooled down VERY quickly!
Here's my install thread.
Buy a dometic non ducted Brisk air II and the non ducted ceiling kit.
Only thing you'll probably need special is a inch lb torque wrench.
Adding a second a/c to a 30 amp camper.
08 duramax tuned n modded
2011 32bhok Sabre
2015 camping "24 nights"