I would suspect the radiator. I have an '83 250 that overheated for years and we would look in the radiator and see water circuilating as expected. After replacing everything else, I pulled the radiator and removed the end tank. The radiator was completely plugged over half its height. I had less that 50% of a small 2 row radiator function. Replaced radiator with HD 4 row and have had no problems for last 5 years.


1961 Chevrolet C-10 Short WB Fleetside 235 Pick-Up, among nemerous other "things"