Aristo Gs 300 twin turbo overheating

Hi
i have a problem with myb engine, after going for 100 miles my engine starts overheating.
i have rememoved the heads,checked found ok, renewed the gaskets and still i have the same problem.what could be wrong?

Low coolant level or air in system - needs replenishment or removal of air.
Lower radiator hose is soft on inside - collapsing under suction and needs to be replaced.
Thermostat not opening fully and needs to be replaced.
Radiator obstructed and needs flushing.
Block cooling passages obstructed and need flushing.
Water pump fins corroded and need to replace pump