A f350 or chevy, dodge 3500 is registered as a commercial vehicle with at least 10,000 GVWR. If you put a shovel in it to go make money (it is about making money) it has to have a DOT number. If any of these trucks pull a triple axle trailer with 8 lug tires (7000 lb) axles they are now a 31000 GVWR and have to have class B license. Class B starts at 26000 lbs. If it has air brakes you have to have at least a "B" license with an air brake indorsement. I think it is at 40000 that the "A" license is required. These toters can be equipped any way you want, but the DOT asks what are you doing with it. If you are making money than it is now a commercial vehicle. A taxi cab is a commercial vehicle and has to be registered as such.