It is my understand from reading some of the Thread on here and others also this is only "in theory", you could reflash your PCM with a 2014 1/2 Mustang GT calibration or a 2013 Boss 302 calibration and then you may be able to get the tracKey to work. After reading the Ford install guide for TrackKey you need a VCM (which some of us have), IDS software with version 75.05A or newer, and it sounds like you need a subscription to proservicetech.com and another key that has not have the PATS set yet. I'll put the links at the bottom so you can read the instructions as well.

I as found that the PCM calibration that Ford is using for the 2013 Boss Mustang is CR3A-SEMABM-5BB and for the 2014 1/2 they are using CR3A-SEMABM-5BC. If you wanted TracKey all the time you would just install those PCM calibration.

TracKey Website

Boss 302 TracKey Dealership Install PDF

2014 1/2 Mustang GT TracKey Dealership Install PDF

 

Actually the problem is the 2013 gauge clusters do not support the functionality that allows for dual key/dual calibration. Only the Boss 302 and 2014.5 clusters support it.

You can either:
-Go with the Track Cal option for 2013s
-Go through the steps to swap your cluster (documented in another thread) and hope the dealer can install the Track Key (their IDS software may prevent this because it knows your car is a 2013 from the VIN#).