I guess this is the R129 car? I don't think I have the wiring and don't even know what car exactly it would be but it probably is close to the W210 wiring where:
A-connector, pin 8 is ground, brown wire,
pin 4 is constant power, red/white wire,
pin 3 is the mute signal, yellow/black wire,
pin 5 is the antenna power wire, blue/white
Cars up to 05/99 also have illumination "signal" on pin 6, grey/blue wire,
speed signal on pin 1, green/black wire and
switched power on pin 7, black/yellow wire.
D2B head unit would have a diagnostics line on pin 2, grey wire (wake up on C connector pin 4, blue/black wire).
Can bus from 06/99 onwards at C connector pins 1 and 2, brown/red and brown wires.
Since this seems to be a car with a CAN-bus based head unit, the illumination wire should not exist on the A-connector, neither the speed signal but the new unit may not need that. It is a bit odd to me if it did have constant power wired to the A-connector from factory but since Shude says, this may or may not exist, I guess it just did on this car even if the factory HU would not have needed it.
Attached the pin assignment for a W203 Audio 10. You can see that the wire colours are not all the same (I thought the constant power should have been red with a blue stripe but still different, like some other wires).