Hmm, I cannot offer much help but I can say that I have had my crankshaft bolt come loose from both of my 603s. My mechanic at the time said he had never heard of that happeneing but to me it had.
You might want to check YouTube, dieselmeken the swedish pump builder had a video for a 606 where he came up with a better bolt solution but it did not provide much information.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k