1985 Chevrolet Truck overheating problem

I have a 1985 C10 Truck 305 engine that overheats very rapidly as soon as I drive it or even if I rev the engine. I have replaced just about everything and I mean everything in the cooling system, including the radiator. I bought a new thermostat and tested it in hot water and it opened fine. I ran the truck without the thermostat and it did not overheat, in fact it didn't even warm up to the normal operating temperature. I put the tested thermostat into the proper place and the truck is back to overheating. Yes, I know the right way to put a thermostat in the engine. Even though the truck is overheating, the radiator hose coming from the thermostat is not as hot as I think it should be. Somehow the water is not circulating. I'm looking for advice from a mechanic with experience with older vehicles who might have seen something like this before.