I remember when I was a teen working with dad in his construction company. His 1963 C60 dump truck was rated at 19,500 and had a 292, 4-speed and 2-speed rear. The quarry roads were rather steep and I used to crawl outta there with no problem at all...and that was tipping the scales at over 32,000 pounds. Probably not a good idea to be overloaded, but the C60's are tough and I never had a problem in the years that I drove it. True, the gearing plays into the equation, but the 292 did everything I ever wanted it to do. Further, if you look at most drivetrain configurations and gearing, most C60's weren't made for over the road use anyhow...
Just some more food for thought
