Isn't that a Chevrolet? The slabsided Mopars and Cadillacs OTOH:
https://heacockclassic.com/wp-content/uploads/8-1-1.jpg
I compare the early BATs to the Sunbird/Road Runner with the towel rack wing. That's a high-aspect airfoil with a lift-reducing wing. The BATs had no trunk lid clearance problems and less downforce. Luigi Colani would roll those fins in just because he could, and I think the slot midspan has some effect in crosswinds. Any vortexes shed are held closely into the wake.