slant 6 overheating

Pop the rad cap while the car is running. Look into the radiator, look for water circulation. Make sure its moving, if not water pump, make sure your hoses don't feel spongy as at speeds the can "collapse" and cut off flow to the block. You can try to flush it with one of those prestone rad flush kits. you can add the "tee" kit and "power flush"with a garden hose. id do all the chaep things first, then if no go pull it and take to rad shop to flow test.If needed have them recore it and hopefully it'll be ok ,