Well, since MB doesn't offer bushings for 3 out of the five rear links, and since I have never heard anyone call them control arms, I mistakenly assumed you were talking about front suspension parts. All the rear links except the bottom one should be replaced as units. If MB doesn't offer a bushing its because replacing it wouldn't be a good repair. besides the links are dirt cheap.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician