Ouch!
It looks like you've got a tight bearing somewhere, sorry to say! I'd start by draining the oil, and strain it through an old pair of pantyhose, cheesecloth, or something similar, looking for bearing debris. Next, drop the oil pan, and check out the rod and main bearing areas for discoloration. Loosen the rods one at a time, and see if it frees up when a particular one is loosened. If not, go to the main bearings one at a time. No crankshaft/bearing problems, it's possibly a tight piston. Not too likely to cause a complete lockup with piston problems, however. Good luck!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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