Between Yellowstone and Glacier, you have several great routes to take. Plenty of Forest Service campgrounds and private ones also. There is the fastest route that is US 287 North to I-90 to Missoula, then US 93 North to Kalispell, but here are a couple more "off the beaten path" routes that are good for your MH.
1. Take US 287 North out to Ennis, then MT 287 to Twin Bridges, then MT 41 to Dillon, then MT 278 to Wisdom, then over to US 93. The route to US 93 goes through ghost towns (Virginia City) and several river valleys that are excellent trout streams (Madison, Ruby, Beaverhead and Big Hole - if you're into that). Pretty country all the way. Then go North on US 93 through the Bitterroot valley to Missoula and Kalispell.
2. Take US 287 North to I-90, then I-90 North to either Garrison and take MT 141 and MT 200 to MT 83, or stay on I-90 to just south of Missoula and take MT 200 to MT 83, then North to Bigfork. More nice country and rivers that you see in movies.
I have been on all of these routes and all the roads are good for RVs. There are some mountains to go over, but nothing like the Beartooth. Have a great trip...
