[V8] CD changer install question

[NicolCS at aol.com]

This has probably been hashed many times but... What does it take to install 
the factory cd changer in a 90 V8?  The car has the later '91-up style 
Bose-Gamma head unit with the "mode" button and a jack on the back for a cd changer.  
I have two of the interface boxes that go near the cd changer and three 
changers.  I also have two or three identical Gamma head units.  The cd changer 
plugs into the interface box - that's obvious.  I used the wiring diagram in 
service manual to make a cable from the interface box to the head unit. That's not 
too complicated, only 8 wires. The only "if" in that program is in trusting 
the pin number scheme molded into the other radio plugs and the interface 
connector.

With everything hooked up, all that happens is that the changer  goes 
"click-click-click..."  I know the changer(s) are all good - I have a Sony RF 
modulator and control and they work well with that control. (It's too bad the 
modulator itself is toast and Sony won't fix it)  All three head units behave 
identically and both of my interface boxes provide the same symptom.  I'm thinking 
that either I have incorrectly connected wires in my cable or there is another 
piece that I'm missing. Anyone know where I could get a "real" cable to 
purchase or copy?  Is there another piece involved?

For the record 
Head unit 4A0 035 192A
Interface 4A0 035 239
Changer 4A0 035 111

Thanks in advance,
Craig Nicol
90 V8Q, 96k, Cinnamon Red/Orange & Black