I had the same problem and I tried it all. New fan, waterpump, radiator, belts, radiator caps 0,4 7 degree pressure) and it still happened to over heat. This went on for two years.
Finally I put on the water pump adapter that fits the 261/235 engine. I moves the fan up a few inches in the center of the radiator. I never have the over heating problem anymore.
IMO: I have tried it all and nothing works better than that adapter. And I installed in while the motor was still in the truck.
