http://www.fordgtforum.com/forums/showthread.php/26016-Motorcraft-5W-50-full-synthetic?highlight=Rotella
They're switching to Rotella T6 5w40 as they say that Motorcraft 5w50 breaks down too fast.
I'm getting ready to do the first oil change. I found this, but $140 seems steep for oil and a filter.
https://lmr.com/item/LRS-6731U/2016-mustang-shelby-gt350-motorcraft-oil-change-kit