410D coupling flange torque setting

Hi all, I'm looking for help with my 410D van (Mercedes Light Transporter). I have to replace the diff -> prop shaft coupling flange. I'm told the torque setting for the retaining nut is critical, but nobody seems to
know what the actual setting is. So I'm hoping some kind person here might be able to please help me out with this bit of information.
Or, failing that, suggest from experience how they've dealt with a torque-less coupling flange situation.
Many thanks.

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