So what you've found is that the coolant pump currently installed on your car is damaged & that is probably why nobody put a fan on it. It should have been replaced when the car was smacked. Don't use a used water pump that's been sitting. They are VERY likely to fail shortly after they're put back in service. Use a new/rebuilt coolant pump and then you can install the fan/fan clutch.

Regards,

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Brian Toscano