To be perfectly honest, it's pretty much what we expected. The teaser photos indicated that the hood was the only major body change, and this car confirms it. The rest of the body is identical to a normal Hellcat. The bumpers, grille mesh, even the wheels are all standard Hellcat parts. Even the slotted rotors and Brembo calipers look the same. This car does suggest that the hood will be available on both the narrow-body Hellcat and the Hellcat Widebody, the latter of which was featured in the teaser images.
There is actually one other minor difference on this 2019 Hellcat's exterior, and that's the grille badging. There's now a vintage-style badge with " Challenger" written in script off to one side. Currently only one grille and badge design is available on Hellcat, and it features just the SRT Hellcat logo. It appears the SRT badge is still present, but blocked off on this prototype. So it's possible this new badge comes with the new hood as a sort of retro package for Hellcat.
We should have all the details on this and other 2019 Challengers when the car is officially revealed later this summer.