OVER HEATING WON'T GO AWAY
Are you using a 3 core or 2 core radiator? I seem to think mine has a 2 core but 3 cores are available ('84 300D). Are you sure headgasket is OK. Have you put a pressure guage on the system. (Probably will need a tech to do this, unless you are Tim the Tool collector) If the headgasket is still putting pressure into the system it will never cool.