As an update -- the Dorman part 604-262 does NOT fit the 2011 Mustang v6. One dimension of the part is too wide, which will not allow the part to line up properly with the mounting holes. The part hits part of the floor vent. I am not willing to try cutting the vent. So going to try another brand, I guess motorcraft since its the same price as the Dorman on Rock auto.
Hope this helps someone.