First, the 8er BMW OEM stock radio was unique to the E31. These radios had the station/disc selector buttons in dual color, have the Weather Band button (under Band), and are integrated with the standard analog telephone.
The BWM OEM standard radios for the 3 and 5 series had a Mute button and none of the things mentioned above for the 8er. With that said, the radios from an E36/E34 will work in an 8er will work with the OEM Pioneer CD unit, even though it was an Alpine unit and not stock for the 8er.
Secondly, there were two versions of the stock OEM radio for the 8er (and potentially a third version).
· For the 1991-93 BMW 850i/Ci's, the Pioneer Model # was: KE-91ZBM (without any "versioning" information; consider it version 1?).
· The Pioneer radio model number for the 1994-97 BMW 8 Series is: KE-91ZBM Version 2 (88 88 1 600 235)
The good news is that either radio version will work in a 1991 BMW 850i. I'd recommend going for the newer version because
· early radios had a glare issue during the daytime; one could not make out the radio station/display information if the sun hit the radio just right; and
· the newer radio head unit is just overall better.
Just in case you need it, here's the Pioneer CD player info:
Pioneer 6-Disc CD Changer w/o I-Bus
Model #MDX-91zbm
Part #82-11-1-467-700
There's a method to find out exactly which Pioneer radio you have by pressing a couple of keys. If you pres "-" (next to "mode") and "PROG" simultaneously, the radio displays its manufacturer (e.g., Alpine, Pioneer) and version. I think your year would come out to be Pioneer 4...which I believe relates to KE-91ZBM Version 2 or 3.
Here are some pix of KE-91ZBM:
In case anyone's interested in a service manual for these radios, they can be found at:
Pioneer Radio Manuals - KE-91ZBM
