Should be pretty obvious that it's based on a HSV prototype (production version).
Firstly, if you look at the purpose of the concept's fiberglass "speedster" tonneau it is there to cover the space left by the removal of the trunk hatch and c-pillars found on the HSV. By removing the trunk hatch and c-pillars of the HSV and replacing it with the tonneau, the rear of the concept vehicle is relatively "flat" in comparison to the HSV, whose rear hatch and center taillight assembly both defines the rear shape of the vehicle and serves as a rear spoiler.
Notice how this rear shape of the HSV is entirely absent on the concept, yet the shape of the corner taillights remains relatively unchanged. Instead of the distinctive "protruding" factory lenses (whose outward protrusion serves as part of the trailing edge of the spoiler shape) found on the HSV, the concept has simple non-protruding taillights utilizing simple LED rope inserts. Note the purposeless vents which occupy "dead space" where the lenses once were.
Also note, the character/fender flare line and it's termination into the corners of the rear taillights. (***Compare Images***)
Lastly, the distinctive doors, whose lower shape which is obscured by a body kit.
