I have an SOB that has a standard window unit as part of the factory install. I like it for two reasons, one is the reduced overhead, second is the reduced cost if the unit has to be replaced, $250 vs $800+ for an RV unit. My SOB is a 16' and uses an 8,000 Btu unit.
You will need some way to exhaust the hot air from the rear and sides of the unit. On my installation they put it in a cabinet up near the roof and used a standard RV fridge vent on the roof, with a plastic screen/cap on the sidewall. It is mounted in some sort of metal sleeve that is mounted in the cabinet.