If it is a flow issue then removing the thermostat may help but I wouldn't recommend it for more than just a test period. Remember that thermostats are there to keep your car from running too cold, not too hot.
I would try the following:
Back-flush and put some kind of cleaner in the system.
and
Check your spark-plugs. if you are running rich or lean you will overheat.
Run a can carb medic through the carb.
and
Make sure your EGR valve is not stuck shut.