Got your PM asking about my search from an old topic. At that time it was right after I'd gotten the car and I'm not totally sure I remember what I was trying to accomplish but here's a guess...
My car came with the McIntosh radio, meaning it also had the subwoofer and amp between the seats. Maybe I was looking to replace the head unit with a more capable system with bluteooth etc.
I was never able to find a connector that would adapt the main car connector to anything, even a pigtail, nor was I able to find a matching connector that I could make my own pigtail. I was unwilling to cut off the wiring harness end connector (in case I ever wanted to revert). It seems the radios all come with a connector the head unit with pigtails and the installers simply cut the old connector off.
I gave up and was actually quite happy with the sound from the McIntosh. I remember driving through Hygiene, CO one sunny Saturday morning and the radio station was playing Comfortably Numb. I literally cranked the radio volume to the max. On most systems the speakers would go into overdrive. Not on the Mac/GT. The sound was spectacular. The only thing that happened was that every pedestrian within a two block area gave me a thumbs up
Oh and it rattled my innards.
So I guess the question is, did your car originally come with a McIntosh or did you acquire the pieces and parts, e.g., speakers, woofer, amp separately and you're trying to upgrade the sound system from the base to the Mac?
The reason I ask is the question of, even if you can find the connector, whether the amp is compatible with a third party head unit...