Its hard to say whats wrong just by explaining it ,I had a friend years ago,who did everything to his car to fix the overheating problem.. well it had bad seals..

Keep in mind,the more you overheat that engine,the chance your housings,and plates wil get warped..

You might want to start looking towards a rebuild..

the water pump is easy to change,if you do that get the thermostat changed,and rod out the rad if its real bad..

But I still think its the seal..pull out some plugs,are they white on the ends?wet with coolant?do you smell burning coolant with the car ideling?