I think I understand the differences for ducted/non-ducted and Multizone units. Ducted multizone apparently has no grill inside, and the unit is a top down mount. non-ducted can be either direct vent through the grill or have ducts and vents in the grill that close off, and ducted can have just an intake grill with no ceiling vents next to the intake.
What I have is the kind with the grill vents and the plenum is sheet metal attached to the unit and the control box attaches to that and the cross member on the ceiling clamp.
Currently my ac unit with the shroud removed is 14" from the top of the roof. So what I am looking for is a unit that is just under 14" at the most with the shroud intact.
Two units are low profile, the Dometic Penguin II and the Coleman Mach 8, but both are at least $1000 without the control unit or grill. However I did find a Dometic unit that is 12.7" installed and is less than $700 for the 15K unit. Now I am trying to find the right ceiling grill and control unit. There is also the option for a heating unit that goes in the duct side.
The install is not complicated in any way, its locating the correct parts for the application that has been a bugger.