I would first determine if your alignment guy knows what he is talking about. Correct installation of the bushings is detailed in the Factory CD ROM where it says that orientation of the bushings is critical. on 124 and 129 models the flatpart of the bushing is on top in the rear and on the side in the front. It is the opposite for 201 models. You can probably go by the dealer and get a printout of the pages. If your control arm has a 124 part number it is probably right. There are 3 dots on the bushings and you can eyeball and compare them with your old control arm to see for yourself. If they are not right I would take the old control arms and the instructions to a machine shop and get them fitted with original equipment ball joints and bushings. Then you could remove the Febi control arms and try to return them for credit.
I am telling you this because I have found out the hard way that Febi parts are junk. I did a complete rebuild of my 84 300SD front end using aftermarket stuff and I still have clunks in the front end and can't get enough caster to meet front end allignment specs.
I won't let that happen again. When I re do the front end on my 92 300D my plan is to use original parts (which really don't cost much more)
There are several discussions on the forum about Febi Parts. Do a search and check it out.

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL