I'm with P.E., I expect that the engine that ran out of oil will be more expensive to rebuild. I would rebuild the tired engine.

I would bore the existing sleeves and use the first oversize. I think P.E. is being optimistic when he says that the power gain from maximum bore size would be negligible, I think it would be completely non existent. You are not dealing with a gasoline engine here.

You can indeed sleeve it back standard, but with such high mileage pistons, I personally would not reuse them. I have on a shelf in my shop, my momento items, among them is a high mileage 616 piston with failing ring land. I caught it just in time. The pistons in a diesel are highly stressed items. For this reason, boring and using new, first oversize pistons is the most economical, practical way to go.

Good luck,