like Greg suggested, check the piston pins and adjacent bearings at the top of the connecting rod. I know you don't want to pull the pistons, but you might have to. One possible alternative - mount a dial gage so that it rests on the flat bottomed surface of the con rod(s), and try to pull the con rod up and down to see if there is any play. Maybe you might be able to flush the journal with rubbing alcohol and compressed air to remove the oil film so you can measure the play. You shouldn't be able to measure any play unless you have one heck of a gage and technique to match. The fit is something like 10 microns IIRC?? Anyway, if the rod bearings are scored due to insufficient oil, it's a pretty sure bet that there was low oil to the rod to pin and pin to piston fits. Plus, the width of your ring grooves could have opened up. This is a very cool engine to rebuild, but, a good used engine is sure a nice option.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.