If you are hauling heavy and planning to do it full time and do not have to drive ice roads in the winter I would give serious consideration to getting a 1A license (that is what we call a tandem axle unlimited weight airbrake license in canada) and forgetting about the weight problems with pickup derived tow vehicles and the underpowered medium duties. For the price of a new or near new loaded up 1 ton dually you could get a really clean class 8 with 475 - 550 hp and 1600 - 1800 lbs torque with a 13 speed. That truck would last forever.