... road conditions and weather. May be be snowbound in a motel for a couple of days.

The sooner, the better.

First off.

There are some private places along the way and once you get into Montana, there are fishing access points along the Yellowstone River, which you would be following if on the Interstate. They are run by the state and many have camp grounds, you wont have water but they have vault toilets. Depends on what accommodations you need. Only buy groceries in cities.

USE A PAPER MAP or ATLAS. Do not rely on electronic mapping apps or devices, stay on paved roads that are on the paper map. US Hwys can be a good option in some places because the access is less limited. The campgrounds I mentioned are on the paper map.

Watch the national/regional weather for a few days to plan you drive days, don't get caught out in the middle of nowhere in a blizzard. Also, the wind is really stout out here so keep that in mind with your vehicle.

Very helpful.