So how will you know just which S550 you're looking at? There are subtle visual cues that should help you discern.
Notice the Tribar pony logo on the rear fascia. The tribar pony has been a staple on the V6 for some time now.
From the rear the differnce on the Ecoboost should be the galloping pony by itself absent of the tribar...
If you cant tell its a GT by the big GT slapping you in the face out back, you should be able to confirm it by the 5.0 badges on the front quarters. Also of note the GT will have twin nostrils on the edges of the hood. No word if the Ecoboost performance pack will also feature the same...
2014.5 Launch Model
The 2014.5 Mustangs will be discernible by three key features. One is the pony in the corral on the front grill, this harks back to the original '64.5s grill, same story for the wheels they are special for the 2014.5 as the mimic the original launch wheels from 50 years ago. The last is not as easy to tell off the bat, the 2014.5s are rumored to be painted in retro wimbledon white, just like the original.
From the front I don't think there will be any visual dichotomies between the three trim levels, out rear all will feature true dual exhausts, as well as the aggressive diffuser.