The HD Silverado and its twin, the GMC Sierra HD, are designed for heavy towing and hauling. The 6.0-liter V8 and 6.6-liter turbodiesel are both mated to a six-speed automatic. The latter works well and employs a heavy-duty Allison-made transmission. A natural-gas version of the 6.0-liter V8 is also available. The LTZ trim has a luxurious cabin. If you don't plan to go off-road, the Z71 suspension is superfluous--it severely degrades ride comfort. These HD pickups are the better choice for commercial snow-plowing duties.