Don
Sorry to hear this news! Don Jr. just doesn't seem to have any luck with this car. My Mustang in High School was like that. I rebuilt the engine, but it never sounded right or worked right! Turned out to have a 302 crank in rebuild kit instead of a 289. After letting it sit, and amost getting killed on my motorcycle, my oldest brother, bought a 289 used and dropped it in the car as a gift. I was back driving it , proud a a kid could be, until the idiot light lit up on the highway closely followed by a loud clank, of a thrown rod. I gave up and sold it, still makes me shy away from Mustangs, though I still love them. I feel for him. Hope whatever it is, it is readily fixable.