Ford common-ground speakers

I have a 1993 Mercury Sable LS wagon. I'm trying to put in an aftermarket CD player. I purchased a wireharness adapter but, the problem I'm having is the speaker harness only has 5 wires since it's
a common ground system, I need to adapt that to work with a floating ground (each speaker has a ground) system. I haven't been able to find the wiring harnesses anywhere. Anyone have ideas?
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====================If it really is a common ground system (odd on that new of a car, are you sure you arent overlooking another plug or something?) you will have to run new wire to the speakers.
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Yeah, I'm sure it's a common ground system. it really is confusing, my 91 Taurus didn't have that. Some of the "premium" systems used a common ground, this has premium sound, but apparently no amplifier, unless it's hidden somewhere else on the car.
The factory radio has two plugs, an 8 pin and a 7 pin, the 7 pin connector has all the power, dimmer, power antenna and the 8 pin is speaker/remote. Now, this sytem has a remote, but, it seems that's a 1 pin plug (don't ask me).
The 8 pin plug contains all my speaker connections. On the aftermakret adapter the positives for each channel match up, but, there's only one ground.
My main problem is I can't find where the wires come into the car from the door, or I'd have already wired up new connections.
-Jay
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