Mine is the standard BMW radio, and only has one slot-type connector. It's the tape/radio type. E30 318i Saloon.
If it's likely to be it, I'll fish it out and photograph the top of the radio, which has got a wiring diagram (although i imagine you've already got that).
All I can remember is dark blue is ariel signal lead (+12 and ignition = up, 0 = down)
Unmodded (and never will be) E30 318i