Did you remove the petcock on the drivers side of the engine to see if that was plugged? 235's have a tendancy to build up rust/crap around the rear cyl which would make it run hot. Open up the drain, if plugged get a coat hanger and go to town. When refilling the block with your antifreeze/water solution, do so with the top part of the therm off, that way you can fill the block and head with antifreeze without air. Then put therm in and reattach hose.
