Well, it's the roof skin from a 68-70 Charger.

According to an article I read about it, it's a fabricated body on a mid-engine chassis.
The intent was to crib a lot of musclecar body styling features.
It supposedly sounds wicked, but they didn't post a sound clip of it.

Supposedly bat man was a street racer and that was his charger, then one of the racers was killed by the joker or some other villan so he up the ante on his car and turned into batman lol. I looked into the car, the rear engine is a ford triton V10 but I dont believe it actually runs. They built 5-6 cars and most are "conventional V8 powered (350 or LS) and one is tesla powered to be used indoors and for night shoots where noise would be an issue.