Take power from the reversing light but before you feed that power to the camera, run it through a power stabilizer. Otherwise the image will come out with bad signal. The stabilizer units are mostly made in china, are cheap to get, and from my experience, burn out after about a year so dont worry too much about it's placement. Put it under the plastic trunk lid cover and tie it to something with tape, like next to the trunk lock/unlock mechanism, so you can easily change it when needed.
