Joe,

Have you tried Co-Pilot? It is designed for truckers. I think you can deselect the Interstates in your route planning. You input your desired speeds on Interstates, secondary roads and roads through town, also height weight and length. It will not take you down a road that is weight or height restricted for your rig. I like it because it trip plans for your speeds and will show truck stops and fueling stations, etc.

Doug