Hey Everybody, I am making this post to bring you all a factory amp wiring harness pin out diagram. I've seen it asked for so many times, plus the information I've got from everybody here, figured it's time to give back.
*Notes for Noobs or electrically challenged*
Its Not good practice to re-use the +12V or GND on an aftermarket amplifier, The wires are old, and too small for the current new amps will draw.
If an Aftermarket head unit is used, Run some RCA's to a new amp. Cleaner Signal and its easier if you are already running a new +12V.
Use the same gauge wire for the +12V and GND.
Make the GND wire as short as possible by bolting to chassis close to Amp location, to help avoid a nasty buzz. (You remember your first drunk on moonshine)
I made some pigtails to connect a new amp to the harness, basically 14 ga speaker wire with a fork terminal on one end and just soldered on the other end. The soldered end will act as a pin to push into the harness. Dab of hot glue to holder.
Alright Enough blah blah blah, Hope this works...