Glacier Park--From I-15 to West Glacier you can take Hwy 2 to West Glacier. Last time we were their we stayed in the park at Fish Creek no hook ups, at that time we had a 36ft MH. Another time we stayed at a KOA in West Glacier. A nice day trip is to go to Whitefish, it's a neat little town. Also you CAN'T take your RV across the Hwy Going to the Sun.
We have been on Hwy 83 and 93.
Yellowstone -- We like West Yellowstone, we like staying at Madison Junction (no hook ups) at West Thumb in the park. In the evening you can hear the Elks, and they walk through the campsites. You can get in your car drive back toward West Yellowstone about 3 or 4 miles to see the Elks there too. The last time that we were at Yellowstone we couldn't get in the campground, very disappointing. We stayed just about 2 miles north of West Yellowstone, I think it was a forest service it was nice. I like to shop and West Yellowstone is cute. We have stayed at Fishing Bridge at the RV park, it's OK. We enjoy driving around everywhere in the park.
A nice day trip is Nevada City and Virginia City.
If you want to do a side trip up or down from Glacier to Yellowstone you can stop at Lewis and Clack Caverns it's near I-90 between Butte and Bozeman they are nice to see.
Grand Teton--- we stay at Colter Bay, we also like drive to Jackson
A side trip is Cody WY Buffalo Bill Historical Center and Trail Town. The Hwy 14,16 20 is good from Sheridan
Rushmore --We stayed near Keystone. We like to drive around a lot, must drive the Needle Hwy to Iron Mountain Rd you will see the donkeys. You also can see the Wind Cave NP and Jewel Cave NM.
I retired from AAA I worked in Touring and Travel.
We went back down to a 32ft MH much happier.