I just checked the MB fiche and a 1989 260E and 1989 300CE share the same caliper, different steering knuckle.

A 1992 400E has entirely different calipers and steering knuckles for both the 260E and 300CE.

Again, I would change out the steering knuckles or the entire hub assembly from the same year 400E.

:-) neil
1988 360TE AMG
1993 500E

PS: in order to upgrade from wagon calipers to 1993 500E calipers, I had to install 400E steering knuckles/hub assembly.