I had Best Buy put a Kicker system into my 2013 Taurus SEL. They pulled up a spec sheet for the Taurus that told them which two wire colors to tap into behind the screen to get their right/left audio outputs to the amp. Don’t try tapping into rear speakers, the sound quality will suffer. The spec sheet pulled is for a 2012 Taurus with MFT and push start, so I’m not sure if the wire coloring is the same for your 2016.. and, your interceptor likely has the small screen instead of the full-size My Ford Touch (MFT) system, so your wiring scheme may be very different than the picture of the spec sheet.
As long as you have someone who knows what they’re doing, it’s doable. I watched them do it and even took it back apart myself a couple times (had intermittent crackling/popping, so I thought there was a loose wire. Turns out, the guy who installed it reversed polarity when he tapped into one of the wires). If you use a professional, or know a lot about wiring yourself, you should be fine. If you want to DIY it, it might be worth a shot to ask a Best Buy Car Audio Tech if they’ll print the sheet for your 2016 Interceptor, then you’ll know which wires to splice into.
as mentioned above, you have to tap into the front speakers to get audio. This is done with a special converter (that i forget the name of at the moment) that allows you to convert the audio wire splice into the RCA jacks needed to run to the amp, its like $20 even if supplied by whoever does the install. I had the wiring in my 2010 and 2015 both professionally installed. 2010 was Best Buy and 2015 was an actual audio shop. I just dont know enough about wiring to even dare do it myself, so i figured i might as well let the pros do it. Plus that way if something goes wrong, they have to fix it. Example, in my 2015 most recently the audio shop broke one of the runners when installing the wires so they had to replace it. If i did it myself and broke it, i would have been out that extra $100 or whatever the dealer charges for it retail.