Even two row chain on 3.0 OM642 already worn around 300-350k miles...OM651 has timing chain in the rear. I hear that single row chain is no longer lifetime item on those diesels, but nobody come with solid conclusion at what mileage we should worry about it.
In my search for Sprinter I run into couple of them with 600k miles and still "running strong". But listings had no records.