1984 300D W123 speaker and decks?
 

Did some searching, apparently the fronts are 4" and the rears 5" :confused: Is this correct?

Also read that the fronts are a weird fit, but I'm more than fine with modifying the existing area to get the installed. Has anyone done this with success?

What about the rears, can a 5.25" be stuffed in there easily?

See separate thread, "W123 front speaker removal"
 

This very subject is currently being discussed on another thread on this Forum, "W123 front speaker removal". I don't have anything to add to what's said on that discussion thread. You may find it to be of interest.

-MW

http://www.peachparts.com/shopforum/car-audio-multimedia/104659-w123-front-speaker-removal.html

Found it, thanks a lot! :D