The 2025 GMC Sierra 3500 HD Chassis Cab is a workhorse that delivers uncompromising performance. The Sierra 3500 HD Chassis Cab offers two powerful engine choices. The available 6.6-liter V8 Diesel Turbocharged engine cranks out an impressive 470 horsepower and 975 pound-feet of torque, while the standard 6.6-liter gasoline V8 generates a still-robust 401 horsepower and 464 pound-feet.