Wtf?

[85rx-7gsl-se]

Hey guys, my dad just got a 83 FB with 12a. I think the motor locked up. It drove fine last week and started just a few days ago. When I tried to crank it today, nothing. Pulled the starter off and had it tested. Its good. Then I tried to turn the motor over with a ratchet and socket. I pulled the plugs out to make it easier and the starter is still off and the tranny in neutral. I cannot get it to turn over either direction by using the ratchet and socket. Any ideas of what has happened? Broken seal wedged? Bearing failure? Any advice is greatly appreciated. Thanks in advance.