Apparently, GM doesn’t understand the meaning of “no.” The automaker, particularly its Chevrolet brand, is again challenging Ford to a heavy-duty showdown. This time, the challenge is going to be high-altitude heavy-duty towing and brake testing in the Colorado Rockies. When Ford respectfully declined Chevy’s advances, GM asked PickupTrucks.com and Diesel Power Magazine to help in objectively pitting the Chevrolet Silverado HD against the Ford Super Duty. Check out PickupTrucks.com for more developments, and read the latest from Ask.cars.com and MotherProof.com as well.