Well, the wait is over - Girodisc 2 piece rear rotors for the bigger 2013-14 GT500 size are available through @OPMustang Tim !
https://www.opmustang.com/store/p43...ting_Rotors_for_2013-2014_Shelby_GT500.html#/
https://www.opmustang.com/store/p43...ting_Rotors_for_2013-2014_Shelby_GT500.html#/