I recently bought a 66 mustang. While on the freeway the engine died. I pulled over to the side, checked under the hood and tried to restart the engine. I heard the revving sound, like the starter was turning the crankshaft 3 times. After the third time I only got and still get a click/thud noise. I thought the engine might be hydraulically locked so I removed the spark plugs and tried to bar the engine over. I wasn’t able to and don’t know what’s wrong. Any ideas before I open the engine up?