If you really want to get away from climbing, go from Cody to Thermopolis, through Wind River Canyon, turn left at Shoshoni to Casper, take I25 north to Midwest and over to Wright, turn left and go to Gillette and then over toward Devils Tower. Almost no hills and not very pretty. Best route would over Tensleep pass, which you would access by going towards Thermopolis and going to Tensleep and over the pass. I have done it a number of times pulling our boat and have had no problems, although the boat isn't a 26'TT and I have a diesel pickup to pull it with.
