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STAR TekInfo

Per StarTek, A and B are the high and low pressure size connectors, respectively.
They are different sizes.

Fuel rail also has a valve for testing fuel pressure but the cap should be made of brass, not plastic.

 

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As for the Tranny mounts confusion ,correct but thats why i added it's for 600SEL ,those are all early 90-June 93 , but i'm pretty sure the Prt #'s must still look similar to the later once ,dont know

The trans. mount beginning with 140- has been discontinued and MB will sell you the part starting with 220 (2202400218 for example)

Sedan or coupe does not matter.

With some luck, Lemforder NOS parts can still be found

 

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Welcome to BW. Be careful with the engine mounts, only original ones or NOS Lemforder (BOGE).
Anything else - you'll be doing it again in a few months.
$640 is unbelievably cheap even for labor only. This is a bear of a job on the M120.

Vibrations --> start with rebushing everything, front and back. Idler and steering arm. Etc.
The prop shaft center support is often overlooked and at 25+ years young likely needs attention

MercS600 gave you awesome advises before, but he confused the earlier style transmission mount (the 722.3 transmission) with the later (the 722.6 transmission). Yours will be different from his.

Good luck!