Ok, I installed a 94 SC engine into my mustang. before doing so, i had the entire engine rebuilt. When i installed the engine, i used the flywheel from the mustang and not the super coupe. I drove it for about 150 miles, vibrating like crazy. I would say half easy on the engine, and half beating on it. Turns out that the supercoupe is an internally balanced engine and the mustang v6 is externally balanced. So, after reading how vibration can damage the crank bearings super fast, should i just pull the engine and have the bearings all replaced, or wait and see if it granades itself to pieces??? what are the chances I caused engine damagae in only 150 miles??? What a bumber to break in a new SC engine with it tearing itself to pieces from the very beginning. I did replace the flywheel with the correct SC flywheel and everything currently sounds good with no vibration.