FYI I checked with MT props - no STC available for the pressurized H models. Aviation Enterprises is currently working on it and advises to check back with them in a few months.
sales@cessnaskymaster.com
I noticed that most 337's with the STC are fitted with white MT's - I would think black ones might at least look cleaner longer given what tends to fly off the rear engine especially if you top off the oil for a longer flight.