I'd try to get to the rubber boot/grommet that has the stock wiring harnass, and feed then through that. You should be able to pull the grommet from both end and feed the wire through and then it''s a matter of fishing the wire through door and getting at it, and feeding it to where you want it.
Firefly: Mal: You don't know me, son, so let me put this to you plainly: If I ever kill you, you'll be awake. You'll be facing me. And you'll be armed.
