You are going to want one of these Audiocontrol LC2i, LC2i - AudioControl
Not only does it give you line out connection but you get dedicated rear speaker output, adjustability to your bass channel and a remote turn on without having to splice into the factory harness to find one.
2012 GT Grabber BlueBoss 302 Intake, 85mm throttle body, JLT Carbon fiber CAI, Magnaflow O/R X-pipe, Roush Axle back, Barton Shifter and bracket, See "My Garage" for an extensive list of mods.
1991 Mustang GT 347
2016 Challenger SRT 392
2010 Challenger RT