By connecting rod bearings.. do you mean rod to crank only... or rod to piston pin also ?
Because of the way in which you can open up the engine you get to see the crank and crank/rod bearings first... so if you find something obvious which can be fixed there you have the option of leaving the pistons and rings alone...
But now it looks like from your description that you will need to go further and check the piston to pin fit and the connecting rod to piston pin fit...
These are the smaller surface area and higher load positions in the stopping and starting the piston the other direction and the first place the combustion pressures impact a bearing surface... 2000-4000 TIMES PER MINUTE... a lot of action happening there... that is why tolerances are so much more important on a diesel than a gasser... 8-10 to one compression ratio compared to 21 to one...
This is the point realistically that you should consider that other used engine you had a lead on..... from what you describe this will be a total teardown if you decide to continue.. which means finding competetant Crank working people... not easy.. and surely very expensive... and this is without the potential piston costs..
Consider bailing on this engine and turning it into that winter project you talked about...
He ordered a bunch of plastigage... so I am sure those measurements will be forth coming.. although much of what I said about the crank still stands...