of those three, I would go with the last one.
the first two are gasket supplements. not replacements.
John
neither would be my choice though. I would go with permatex Ultra Blue. Ultra black is OK too, but the black you have will work, it's just not as good, so be SURE you have cleaned both surfaces REALLY well, I mean after scraping, and wire wheeling, rub really well with acetone. GET VERY CLEAN! and let the goop partially dry after you put it on the Diff cover. then assemble loosely, and only torque after setting overnight.

John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

perfect - thank you. ill go out and grab the ultra blue variety tonight.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

To further clarify, they're also not "silicone." I dunno if Mercedes have any bolt threads that go into areas with oil or coolant, but if so, #2 is a good choice to use on those threads.