Thats is a tough question as some parts will interchange off all 126 chassis cars. Some will exchange on 116 motors. Some parts will be found on all MB models of that year and some will be found on different models and different years. There will be parts that won't interchange between your 89 420SEL and other 89 model 420SELs. It just isn't that simple.
Bosch Master, ASE Master, L1
33 years MB technician