So since I am building my own wiring harness to add the rear speaker leads for speakers in the lowers on my street glide, I was wondering if I could use any of these pins to hardwire in an mp3 player or whatever. Anyone have a list of what each pin does/connected to or does?

 

You probably can, but some help as to what bike you are doing this on would help.

If it is the HK radio check these guys out.
http://www.ironcrossaudio.com/ipod-h...dsonradio.html

 

If you are talking about the Harley 35 pin socket, just use the pins used by Harley.

Here is the part number.
72381-98 Radio Socket Pins

 

I too am wrestling with ipod interface and amp installation and am wondering if anyone has list of each pin's function on plugs on rear of HK head unit.