I've seen a M3 speedo (in German called: Kombi) cluster installed in a 135i. It was in Thorsten's car from Car Coding.de when the guys from the 1erforum.de had a car coding event near me, in Nurnberg.
M3 Kombi instrument gauge cluster...
IF you look closely to the two top screws... this is where the M3 speedo/kombi doesn't quite sit flush. Its really no deal breaker IF you ask me.
Thorsten coded the digital M3 speedo (V = kph or mph) in my 135i's gauge cluster. The KPH or MPH can be changed on the fly thru the BC settings. I really like this "V = kph" feature. It reads TRUE vehicle speed and not the +5% buffered value the speedo reports. But your car coder can also code the buffered value in IF you so desire.
digital M3 speedo in BC menu...
more pics here....
1er Forum Coding Event…
http://www.1addicts.com/forums/showthread.php?t=452070