sentences:  A major factor leading to the cancellation was lack of support for heavy-duty trucks by Chevrolet dealers.In contrast to other GM brands, a key requirement of GMC franchisees of the time was the ability to sell and service the entire GMC product line.In addition to light trucks, this meant a potential GMC franchise needed the ability to support medium-duty trucks, heavy-duty commercial trucks, the GMC motorhome, P-chassis, and school bus chassis.