Other than Yellowstone I would not expect problems with RV space. It's early in the season - it might be a bit chilly at night. You may consider taking I90 to Missoula and then US Hwy 12. Slow but scenic.
We own a LTV Free Spirit with a 2500 chassis and are completely happy with the economy and quality of the unit. The bed has memory foam and is covered with "ultra leather" and we find it very comfortable and roomy. This is one fine class B and we would recommend a LTV to anyone.