I've figure out a solution to this:
connect a wiring harness to a reverse harness and tap the speaker wire to the line output converter. I've listed the items for someone who may be interested in doing so without tapping the stock wire.
BTW, should I tap front or rear speaker wire to the converter?
71-7552 (Reverse wiring harness) - $8
Metra 71-7552 (met-717552) Reverse OEM Radio Harness for Select
70-7552 - $8
Metra 70-7552 (met-707552) Wiring Harness for Select 2007-2008
PAC SNI 35 - $14
PAC SNI-35 (sni35) Variable LOC (Line Out Converter)