Have the same similar issue, radiator keeps blowing its cap. I replaced the cap, the temp sensor, thermostat and gauge. I had the radiator cleaned by a radiator shop just after I bought it this year. It was losing coolant from a busted seam. They cooked the radiator flushed and fixed all the leaks. I then noticed the temp gauge was not working and replaced it after a very long troubleshooting of the wiring harness. Replaced the sensor and the end just fell apart. Thats been all repaired. Not sure if the sensor matches the gauge, It starts out at zero and runs up to 240. but I think I have other issues. The truck runs fine, no white smoke, to cross contamination in the oil or the water. no milky haze on the oil filler cap. With the truck running the radiator burps a little. Not a lot of air bubbles. Even when the thermostat opens up there is not a lot of bubbles. NAPA sells a exhaust gas test to test for cylinder head gasket failures not sure if its feasible on the deuce's engine. We took her for a drive the other night and she ran fine, went filled fuel and the gauge was coming up a little so we headed down the road. 15 miles into the drive the windshield was getting wet from the cap leaking coolant and the temp gauge was at 240. Got to where we where going and pulled the truck over and I shot the radiator with a thermal gun. The top was hot and bottom was 100 degree colder. The thermostat housing was reading the same on both sides of thermostat. I shot the block and found no extreme differences in temp from cylinder to cylinder. Though I might have a head gasket leaking but no definable sign. Is it a blocked radiator, is it a water pump not pumping due to blockage or leaking exhaust gas into the coolant.