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.
I have a 2006. We love it, but it is a POS in terms of body rust. This led to a shocking roof leak. It had absolutely nothing to do with the A/C or any other through-roof fitting. I tell anyone looking at a a 2006 or earlier to be very thorough in inspecting for rust. Mechanically it is great. Fuel mileage is great. The body, not so much.
We also have a 2006 and have never had any problem and we've been out in quite a few downpours. As for rust, we have absolutely none however, it's garaged when not in use and our climate is generally dry. It still looks new.