My guess is that since the engine and suspension components are assembled together, before the body is dropped onto the frame, that is why we are seeing the six piston Brembos in a regular '15 body. I'm leaning towards they are still testing the Hellcat (the reason for the delay to late May or early June). Also, I remember that a lot of sources have said that the "Hellcat" powered Challenger will have a completely different front bumper than the other models, of course 6 piston Brembos in red paint, 275 tires all around, quad exhaust tips, different hood with extractors on either side of the AAR style scoop and different rear and front panels to accommodate wider tires....interesting that the standard non hellcat SRT in the picture also appears to have them, unless this silver car is some in between model, using some hellcat features but not the engine.
I guess we will have to wait until late May or early June to find out what the "Hellcat" powered Challenger will ACTUALLY look like. Because, right now a lot of things are not adding up from recent pics and insider information.