Reverse wire color and location inside cab
OK, here is the +12VDC wire when the transmission is in reverse. This is the main wiring harness below the pedals going through the firewall. The BLACK/PINK wire in the bottom left corner is the one we're after.
Without cutting the wire, remove about 3/4" inch of the insulation from the wire your tapping into. Take a small flat-blade screwdriver, and separate that same exposed wire into 2 parts. Take the wire your connecting to that circuit and poke it through, then wrap it around and around the wire your tapping into. Some people will tell you that you don't need a fuse here, but I disagree. This fuse isn't really about fire prevention, its there so that if something goes wrong with your tap, it doesn't knock out the system your tapping into.
Soldering after you use the "poke and wrap" method isn't absolutely necessary, but it's the highest quality job you can do. I forgot to take a picture after I soldered the tap, but you get the idea.
Next, wrap the connection TIGHT with electrical tape, and work the end of the tape back towards the center of the solder joint. After that put at least 2 zip ties over the tape so that it doesn't unravel over time from heat and cold.
Finally, take your fuse holder and zip tie it down over the solder joint as additional protection against chaffing damage. My final product is neater than this, I tightened things up and moved it around behind the aluminum dash support. I had to take the picture at this point for it to be seen.



