I just did this mod yesterday finally. Worked PERFECTLY. Thanks for the Jack smeister.
I used Cat5E data cable and used 4 of the 8 pairs, used the plenum shielded variety of the cable with is fully shielded just in case (I'm anal about sound system noise).
I soldered the terminals at the jack but I used fishing wire crimpers on the pins on the back of the radio, covered everything with the provided heat shrink tubing (nice bonus there smesiter, thanks, got plenty leftover also
).
Got some pics of the connections on my cel, I'll post em in a bit.