Another option would be a western star 6900xd as seen here: This is a purpose built 50 ton (45 tonne) coal hauler for off highway use. Usually built with allison automatic gearboxes althought this one has an 18 speed manual. As far as a tow truck, I think a push truck would be more efficient, as you could have a cusioned bumper on the front to push against the tailgate of the truck hauling the load, and not have to h
Discuss this in the forum topic Steep gradient coal haulage.