Pictures are from a 98 C70 coupe.
Here's the head unit side


And speaker side


That seems to match BEJinFbk description, I have the grounding wire for the coupe on pin 2.
I cant exactly see where the cable is going, but I'd say it's probably around 50cm/20in long.
You can see it coming from the driver side on this picture from when I removed the dash







