Engines purchased from any of the major salvagers (already mentioned), that were removed from storm damaged (not running or flying at time of accident) are good prospects as long as a flood was not part of the event.
These engines are usually from an aircraft that was being somewhat regularly flow (vs sitting in storage for an unknown period). This can be verified as long as log books are provided (if not that would be a deal breaker for me on any engine)
Another benefit to a purchase from the salvage companies is they will typically guarantee that the case and crank are serviceable.