I've dug around and not found what I need. I have an old '94 C2500 that still has the stock radio. I hung a MP3/USB stereo under the dash rather than lose the shelf in the dash by installing it there. I installed some 6 1/4" speaks in the doors and am fairly happy with it. Only problem is it is not loud enough (gotta fix the AC: at highway speeds with the windows down...yeah, stereo's not loud enough!). I'd like to simply splice into the stock stereo speakers for extra sound. My head unit is spec'ed at 20 watts per channel. Not sure it is putting that out, but hey, it was 25 bucks new. (gotta fix the door locks before I put something good in there!) I don't want to rip out or mess with the stock radio as it works fine...and well...if you know what I'm talking about, you know why I don't want to yank it. I only used the front speaker wires on my new head unit. I'd like to splice into the speakers that are in the B pillars at the back corners of the cab. I know I can just find the wires at the speaks, but I'd rather not re-run that much wire if I can ties into it at the dash. So: what wires am I looking for? Are they simple to find in the harness if I pull the stock radio out to get to it? I'm thinking of just tapping in and leaving them still connected. I don't listen to the radio, but if I ever want to, I can just turn off the MP3 unit and run the radio. Thanks!