Mustang wheels will clear fine. The Mustang Big Brakes are larger than the SHO brakes. I ran aftermarket wheels for a mustang (American Muscle AMR) with no issues for the duration of my SHO ownership
I just put 18" Mustang wheels from a 2012 on my 2016 SHO. I had them for my 2013 with Blizzak snow tires on them - getting ready to head back to Michigan in the morning from our place in North Carolina and decided that some snow tires might be a good idea.