A gas engine falls weak on torque. It needs gear reduction to power a heavy truck. I found mine had 5 X 2 rear gearing. Up, or down hill I was never very high in gear ratio. The engine screamed 3000 - 4000 RPM all the way. This is not good for fuel economy, and a lesser engine won't survive it long. The GM truck engines 366 & 427 were built to haul. Massive crankshafts were forged from steel, not of cast iron. the cooling systems were high volume, big ports, big pumps, dual thermostats, and VERY big radiators! Cylinders were tall, as were pistons, and an extra oil control ring was equipped.
I could brag all day about these engines........until we discuss fuel economy.
I fear newer engines were not engineered for the same level of longevity.