Hi Rich and Joan.
I have a MkII 36 2000 model and fitted an A/C unit about five years ago. Out of all the choices I decided on a Pompanette 16000 BTU model with reverse cold/heat and away cycle settings. The unit fits perfect under the berth in front of the sink and ducts out and up to the shelf on the port side, I have another branch travlling along beside the holding tank right turn into the seat locker of the toilet bulkhead and up the outside of the mast. I boxed the mast in with teak ply and have a duct facing the vee berth and one facing aft. The unit works wonderful and has a soft start which means you can run it with the 2 KVA generator if you are away from shore power.
Because we live in Australia we have not needed the heat cycle, mainly cold or away mode which is a dehumidifier and keeps the mold out on humid days. The unit is USA built in Mass.
To date no problems.
This is our fifth Catalina.
Ivor and Joan C 36 1864