I have been reading this thread for awhile and not commented. In my opinion, your early video of the engine cranking was obvious that this was not a healthy engine. I would never trust a used (unknown) engine without a complete tear down, inspection, and competent machine work done prior to assembly by me or someone I trust. I have built many from the bare block up, including diesels, but I always start with a block that has been checked, bored, etc. by a trusted machine shop. Then I actually do all the measurements myself to be sure. Precision tools, bore gauge, inside/outside micrometers, etc are required of course. I learned long ago do it right, do it once. If your buying a used engine to install in anything, your just rolling the dice. Good luck with your project.
