Susan and Steve,
According to some information that I had from the 2009 model year, the 36RSSB3 in the Mobile Suites has a GVWR of 17,500 lbs. IF it has the Magnum Suspension System with 17.5" tires, it is rated at 18,500 lbs. Keep that in mind when looking at the weights for your truck.
The Mobile Suites would be a better unit than the Montana. They have the thicker walls and insulation, so they would be a better unit should you be caught "further north" than normal during the winter. Precautions still have to be taken, but they are good units. I know a number of DRV owners have gone back to buy other DRV products.
Good luck with your looking. If you are considering the used ones, also check out this website to a used dealer in Elk City, OK that buys the DRV units at auction (usually after a repossession), checks them out and cleans them, and then resells them. They have sold a number of used Mobile Suite in the last year and a half.
http://www.rollingretreats.com/
They may not have what you are interested in right now (both units look too heavy for the Dodge), but keep checking back. Or, you can contact them via their website to see what they might be getting in.
Terry