one other thing to consider - the LS400 doesn't have a rear wiper. so you'll need to put the camera low enough for the defroster lines to clear the view for the camera. i had to mount my a118c about 6" down from the headliner on my camry so that its lens would be next to the top defroster line. my solution for "stealth" was a bumper sticker at the top center of my window, which the camera lens is just below. so a lot like the front, all you can see is the lens itself, and then only if you know what you're looking for.
as for power, i ran the power cord around the edge of the headliner to the front overhead console, where i tapped into the sunroof wiring. this will be much easier than coming down the B-pillars and thrn through the back door hinge and wiring loom. be careful doing this (in headliner) if you have side curtain airbags. you don't want the power cord to be in the way of the airbags if you ever need them!