Blazer won't start

[Powdercoat]

I have a 1972 Blazer with a 1978 motor in it. The motor stopped turning over so I assumed it was the starter. I got a new starter and when I turn the key over the starter will engage the flywheel but will not turn over the motor?? Anyone have any ideas. Oh and the starter sticks in the flywheel it doesn't retract until I turn the flywheel by hand!

Thanks in advance