Missouri Headwaters State Park, right off I 90 just outside Three Forks (no hookups) & Lewis & Clark Caverns, they have some e&w hookups, just down the hill from the Caverns tour.
Glacier Nat. Park is a definite site to see. You need to decide which side you want to come in from. The West is much greener and there are other great places to camp near by. The Flathead Lake region is just beautiful. You really can't go wrong in Montana. Have a great trip.
Mike & Dava
2007 Sierra Classic 2500 HD Duramax/Allison 4X4 Crewcab, Super Springs
2005 Carriage Compass 30RLS, MOR/ryde suspension & Pinbox, Onan 3600LP
Huskey 16K EZ Roller, DigiTrac