If you have lights or speakers in the ceiling, then take out the ones on the center to the drivers side. Remove the camera from the rear cap in see how they came threw the cap into the ceiling. I have rewired a couple friends this way. I have a fiber glass pole that comes in 4 foot sections. I connect a pull cord to it and push from the back threw the rear cap threw the rubber seal into the ceiling area. Screw two/three section of pole together and tape connections. Push from the rear till you can see and touch it inside the ceiling. (helps to have two people). Keep going to you get to the front. Your goal is to come down threw the left side of the front over the drivers seat or in the center of where you need the wire.
If you system comes with several wires you can tape then along the pole as you are pushing it. About ever foot tape on another wire. Use a loop where you tape to the pole. When you get to the front , just pull extra pull string and leave in place for further use.
Going under the chassis will work also, just more wire and you have to secure it more.