just behind the waterpump is the water distribution tube.It is made of brass and imbedded in the engine block.It has a series of holes of different diameters that meter the water flow to each cylinder.They can get clogged easily. Pull out the tube an clean it as well as the cavity in which it sits.Like you,my 1949 288 was running hot .this solved the problem.You can also modify and replumb the heater core to turn it into an auxiliry radiator.