I believe the Reverse Indicator line Tox is using is something he found in the kick panel. I made all my connections to the plug in the roof.
The voltage regulator is rather basic electronics - essentially "in", "out" and "ground". The details of the entire camera installation are here on my webpage:
House of RagE - Road RagE II
You can also save yourself some misery and try to locate a 7807 voltage regulator. That will save you having to mess around with resistors