first of all, make reservations NOW for Glacier.
At Glacier, on the east side, St. Mary has one rv park that gets decent reviews.. Johnson's RV Park. The campground inside Glacier might hold you, not sure.
We live down near Canyon Lake and go up to WY every year, so we have used various routes to get there. If you're not going to Yellowstone, you can take TX 83 or 385.. 83 is probly smoother than 385 in CO, but we still like that route...not much traffic and nice little towns.
When you get to NE, take 26 west over to I 25. If you want to see some impressive wagon wheel tracks, look for a sign pointing to the site in Guernsey..it's about a mile north of town, easy to see with a short walk along the tracks, etc.
Take I 25 up to I 90 and MT.
There is a good rv park in Buffalo called the Indian RV park. There is a small rv park in Ranchester, just north of Sheridan. Plain and simple, in town. http://lazyrcampground.com/
This is a good spot to stop for a couple nights if you want to take your toad and drive up to Burgess Junction in the BigHorns..and also go see the Medicine Wheel a few miles west of the Junction.
Can't help you with an rv park between WY and Glacier...when we went several years ago, we saw several little mom and pop rv parks along 89 in MT.