Since the damage gets progressively more severe the further from the oil pump you go, I'm going to suspect there's a partially-open relief valve in the pump. That would explain why the main bearings were not severely damaged- - - -they get lubed before the rods, which are at the end of the pressurized oil system. The piston probably galled due to insufficient oil thrown off of the rod bearings and little or no oil coming from the spit holes in the connecting rods to the cylinder walls.
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!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!