[mustangman65_79]

This may sound stupid, but di du check to make sure the bolts were tight?

I did this once, on my way to buy a starter, when I got there, and went to buy it, I forgot my money, so went to leave, no start. Went under to try to see if I could maybe get it going again, and found my starter laying on my headers, just grinding on the flywheel. Well, put a bolt in, and I was good to go. Starter was fine.