Sorry for the lack of response (death in the family).
I had planned on tapping the signal wires before the 460 rear amps. It looks like there is a harness back there before them, so I may look into splicing in there.
Before I get the comments, yea I know the box does not fit well and the amp is upside down. But heck, it was all FREE and it sounds awsome (shakes the steering column if I turn it up loud enough).
I have the base centered on the radio, gain controls on the amp are at minimal, the high pass filter is turned on and it sounds great. Nice solid base hits with no distortion and no trunk lid rattle.