The four-cylinder 4BT Cummins diesel engine was taken from a ’90s bread truck with 120,000 miles on it. David put the intercooler between the radiator and engine and then plumbed the piping himself. He also added an electric fan, which freed up horsepower and kept the engine from ever coming close to overheating. The hydroboost brake system is from Performance Online (POL), and it runs off the power steering pump. The serpentine belt system makes maintenance much easier than working on the original 390ci (6.4L) gas big-block. Fuel economy has also increased by more than 50 percent compared to the sparker. The truck now gets around 25 mpg.