The readymix company I drove for two summers, first summer between my Junior & Senior years of college, and then the following summer after graduating. First year drove a year old Diamond REO, nice truck, just underpowered, 208 hp Triple Nickle Cummins hooked to a 6-speed Allison automatic and a 3-spd Brownie. Second summer drove a 10 yr old '66 White with a 7 yrd Smith mixer, 165 Cummins and 5+4 trans. Also underpowered, but the engine drove a BIG hydraulic pump sticking way out in front of the hood.
Company had two '70 White Construktors also with 7 yrd Smith mixers, both had all Super Singles, 185 Cummins & 5+4's, that 20 extra HP made quite a difference in performance, but the super singles did not grip slick muddy ground on construction sites like duals did. It was actually a pretty decent job, always something interesting you poured concrete on. As driving jobs went it was better than most.