I would start with a compression test. I just put a motor in a civic SI for the same exact reason. He went down instead of up and bent a valve, we thought it would just need head work until it was apart and it looked like the valve put enough pressure on the piston to push it up against the cylinder wall and score it badly. I know Hondas will throw a "over-rev" code when that happens and take a snap shot of engine parameters, not sure about fords. He swore that the over-rev happened a few days or weeks before the car actually gave up, but who knows it took a lot of digging to figure out what really happened with that car anyways. Wish you the best of luck!