On the Super Pursuit Mode car (same trans am), several trim pieces opened up, extended, raised, etc to create more wing surfaces for downforce. Some of them would be almost unnoticeable in a side view like this - the rear spoiler and front-clip split would be the only obvious changes. I think personally that it would interrupt the serenity of the composition, though, and you should stick with the standard car. These triptychs have an almost art deco quality about them. I love them, wish I could get one for myself.
Even a solid black car can be done well with a lighter color above the beltline and on curves, as you've shown with the Batmobile. Oddly, I think the Batmobile should be more "black" but it looks really great in the greenish cast you did, too. KITT was very glossy, though, and so will definitely have a different appearance to the flat black Bat.