1995 Ford F-150 Starter not disengaging?

I'm having the same problem with a 1987 Ford E350 with a 460 auto trans. I just replaced the engine with a used one from a 1988 ford F250 with a 460 4wd auto trans. and now the starter won't release from the flywheel and it is making a bad grinding sound. I searched around on the net a little bit and it looks like all the 460 from 84-91 list the same part numbers for the starter, and flywheel. my old starter had some movement in the shaft and sounded like it was grinding a little so, I replaced the it with a new one from Auto Zone. And it still dose the same thing. There is no adjustments to be made with a ford starter like a GM starer. It should just bolt right up and that's it. So now I'm not sure what to do. I don't work on fords that much so if you have any ideas please let me know.