At the Q&A session with Keystone Montana, it was said that the Trailer King ST tire would be the tire used if not already on Montana products other than Big Sky Goodyear G614's.
The Trailer King tire comparison to Goodyear Marathon is
Tire Size LR/PR Tread Depth Rim Width (inches) Section Width Overall Diameter (inches) Maximum Load (lbs) Inflation Pressure (PSI)
Trailer King
ST235/80R16 E/10 10/32 6 9.3 30.8 3520 80
GYMarathon
ST235/80R16 E/10 10/32 6 9.2 30.7 3420 80
The Trailer King tire, while an ST has 100 lb higher capacity than GY Marathon. Tredit has indicated that the Trailer King brand is part of the TBC Corp which is Tire Kingdom and other entities...
http://www.tbccorp.com/. The Trailer King tire is on other RV products but will be or is coming to the Montana line. FYI.