Just a guess, but I bet the reverse "scoop" on the roof is some kind of rear view system, perhaps even a television camera. The GT40 books often note that H-M supposedly installed a camera in a Mk II in the 1970s for a customer, and I recently tested an Infiniti FX45 ("crossover" SUV) that had a camera mounted below the rear bumper that was hooked into the navigation system video screen. Putting the gear selector into reverse activates the camera. Instead of twisting around and looking out the rear hatch window, or using the side view mirrors, when backing up, you simply look at the video screen on the dash. The screen is calibrated with markings that indicate the distance to an object behind the car. This system certainly seemed to work nicely the few times I used it. If there is any car that needs help with rearward visibility, it's a GT40!