here are some pictures of how the "kit" looks like:
the iPod holder will be attached using double sided tape to the "phone holder" that houses all the interface electronics. On the bottom part is the switch; 3 way for off, charge and charge + play. Also to the left of the switch is the additional AUX-IN to connect any other device.
I finish that late because there was a terrible setback. What follows is very technical, you may want to skip. It looks like when i did the initial testing the oscilloscope was set for AC, and i did not test enough, but the signal at the input for the pre-amplifier is ridding of top of 4VDC (probably to a use single ended power supply on the radio). There are some more details that explain why it initially worked but this problem at 1 AM was a terrible setback. It can be solved technically, probably a few OP-AMPS but that will send the design back to square one and i wanted to finish and close this chapter.
Since the radio interfaces in an analog way to the external CD-changer I decided to test if I can use the signal conditioning used for the CD-changer to adapt the signal form the iPod. A brief test confirmed this, but some additional modifications will have to be performed to the radio. The changes were pretty clear in my mind but decided to wait and get some sleep before doing the surgery. This will also create an additional compromise, the trunk mounted CD-changer will not be usable after modifying the radio. I wanted to think a little bit more before committing to this change.
Next morning I decided to go ahead and modify the radio to use the input stage of the CD-changer to pre-process the signal from the iPod. I do not own the external CD-changer, and in any case the changes are reversible. Some images of the changes here, 1, 2, 3.
As soon as I complete testing i will explain in detail what needs to be done and why.