I have a 72 service manual for my Cuda. It lists possible causes of overheating: blocked radiator air passages, incorrect timing, low engine oil, incorrect valve timing, bad temp gauge, restricted overflow tube, faulty rad cap, frozen heat control valve, dragging brakes, excessive engine idle, frozen coolant, faulty fan drive, faulty temp sending unit, faulty vacuum bypass valve, overfilling, insufficient corrosion inhibiter, blown head gasket, broken or shifted lower hose spring, low coolant level, collapsed rad hose, fan belt lose, glazed, or oily, air leak through bottom hose, bad thermostat, water pump impeller broken or lose, restricted rad water passages or restricted engine water jacket