2013-2018 ATS. Rock Auto doesn't have a core charge for those and they are brand new, whereas other more popular ones like Mustang require cores.
The CTS has a different caliper for a larger rotor and won't work well with the smaller 13" rotors. I got my brackets roughed in yesterday and am making adjustments to my CAD file. I'll start a new post on this once I get things wrapped up.