You don't need any RTV or Make A Gasket.

Be Very,Very careful Torquing those Bolts!(You're putting Steel into an Alloy)
If the FSM does not publish torque specs for that engine's Vacuum Pump Bolts,
look up the torque based on the Diameter of the Threaded portion of the Bolt.

MB does not provide Torque figures for the 601,602,603 series engine's pumps.
But I seem to remember 6-7 Nm.

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'84 300SD sold
124.128