Won't Start please help

ok I have a 94 thunderbird 4.6. I bought a junkyard motor for it. I now have a 95 4.6 What it is out of I don't know. My starter off the 94 is not ingageing the flywheel of the 95. All I am getting is a loud screaching noise. I bought another starter installed it same thing. Loud noise no movement. Motor will turn when it is hand cranked not frozen. everything that is on this motor worked on previous motor. would there be a difference in the flywheel teeth or what. any help is highly appreciated. Thanks

maybe the flywheel itself is worn down or something similar?

Possibly different. You might need to find the starter of that same car that the motor came out of.