I've rebuilt many of W126 FE and failures will occure in this order:

Shocks (nothing but Bilst otherwise disapointment)

Guide rod bushings

Lower ball joints

Tie rod ends

Upper control arm/ball joint

Lower control arm bushing (pretty robust lasting a few hundred K miles)

I'm sure there will be some 'expert' chime in but I have owned many of these cars since new and continue to drive two on a daily basis.

Oh yea, the steering box is crap. Usually sloppy at 100K.