76 dodge d600 radiator

I looked it up in the '77 D-series truck FSM. It indicated that the type of radiator depends on the engine, not the truck model. In other words, a 440 in a D-600 takes the same radiator as a 440 in a D-300, and a 361 in a D-600 takes the same radiator as a 361 in a D-300.