Best would be to find somebody scrapping an MC8 or 9 and pull the entire HVAC defroster system out of the dash and re-install in your coach. Call Luke in NJ to see if he might have one: 1-888-262-2434
MC-9s came from the factory with Driver's A/C, so no sense trying to re-invent the wheel for the dash components - especially since OEM is properly sized for the dash.
Figure out a way to drive an automotive compressor off the OEM compressor pulley on the 8V, and hang a condenser on the curbside transmission access door.
Welch Industries in Stockbridge, GA (outside Atlanta), has done a lot of custom bus A/C work, would also be a good source for help.
FWIW & HTH. . .