When I replace lower control arm on a 124 chassi do I have to mark something up or just take it apart the eccentric bolt and change the control arm.
When I tighten the eccentric bolt the car need to stand on it's wheel do I tighten to a specific torque or do I adjust the camber with the eccentric bolt torque.

Take the old arm off, and install the new arm. Tighten everything when it is on the alignment rack.

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

Don't tighten the eccentrics until the suspension is fully loaded, or else you'll damage the rubber bushings. Do a search - there is plenty of discussion of W124 control arm replacement here.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280