To replace the W123 door striker plate (and perhaps valid for other models)

Note that the plate with the threaded holes floats behind the door frame(jam). Not accessible if it drops down.
SO, get yourself a coathanger and cut three or four 7" straight pieces. Enough for each screw hole.

Bend a slight/shallow hook on one end. This acts as a catch and aligner, just in case.

Take one retaining screw out and insert the wire in far enough so that it stays in place. The shallow hooked end goes into the body and the straight end out toward you. The idea is to progressively do this same action with each screw removal in order to keep the internal threaded bracket aligned and where it is supposed to be. If it drops down I have no idea how you can get it back.

Slide out the faulty striker plate out over the straight wire ends.
Keep your wires steady to make sure that bracket does not fall down !

Do everything carefully in order to not loose your bracket!

Slide new striker over the wires via screw openings and begin re-assembly carefully removing one wire and attaching the screw into retaining bracket.
Use the hooked wire to position this floating bracket to screw threaded shaft. Screw in one at top and one at bottom.
Continue with the rest and don't overtighten because you want to align the new striker to the dirt shadow outline of the old one. (So don't clean the door frame after removing the old striker.)

Well this is how I did it.

Fun thread

THANKS

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD