The only difference between the air suspension models and steel spring cars are the lower control arms and the rear axle tubes, (the diff case too based on no compensating spring). The kingpins, upper and lower mountings are the same. The upper control arms are the same. Bushings are similar too and there are minor sway bar variations.
When I look for parts, I find no parts listed for W111 cars, but many for W113 parts will fit as well as W180's. Watch those coolant hoses though.