When lives are on the line, having the right equipment is crucial. Express, Savana, Silverado and Sierra 3500HD key features include: heavy-duty battery, rear heat and air conditioning provisions, and GVWR packages starting at 9600 lbs. through 14200 lbs., and four engines choices including the DURAMAX 6. Also available are: rear-seat A/C connections, dual batteries, a VNF battery isolator, high-rpm PROM for automatic throttle control, seal through cab cowl for equipment and control wiring, and the M74 Allison 1000 EVS Emergency Vehicle Series transmission.