What kind of vibration are we talking about? Is the engine idling nice and smooth and you're just getting the vibration of the cylinders transferred to the chassis? Or is there an irregular rocking or lurching to it?

If the latter, there's likely a combustion imbalance at the root of the problem. A fresh engine mount is fairly stiff in comparison to the old one and will transfer a rocking motion better to the chassis. The engine mounts in these vehicles is designed to restrain the engine and isolate vibration from reaching the chassis. They're NOT designed to isolate a rocking motion. They will damp it, but not prevent it.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]