As suggested above, maybe an ACA route is right for you. Note, however, that the TA from the Oregon coast to Rawlins, WY is 1,667 miles, or about 60 miles/day for 28 straight days with no days off. Moteling it can also take some advance planning as places can be relatively small and fill up in certain places during certain times of year. But one advantage to also having camping gear is that it would be easier to avail one's self of cabins at private campgrounds. I ended up staying in a really nice one in Troy, MT a couple of years ago because the tent camping was occupied by a large group on a supported tour. The place had every amenity of chain motel (including a hair dryer) other than a private bath.