Craig, you're probably right. I don't know what purpose the fins are for, but I modeled them. It looks less like a rabbit:

I don't want to sound like a Negative Nancy but I think you've got the body shape wrong, too, Frank.
I thought something was off in the earlier images but this last one confirmed it for me.
I don't think that curved line at the front is for a "wheel" arch for a non-existent wheel. I think the body bulges out wide from the nose & blends in to the rear wheel arch, & that the curved line is a decorative panel ridge of some sort.
I say this because, in the original image, the line comes out from behind the curved feature at the front & there is no indication of a different curvature to that of the centre section. It probably makes for a somewhat more complex blend of curves into the rear wheel arch but it makes more sense, to me, given what I'm seeing. Especially as the cabin appears to be wider than your rabbit car's.
It's a lovely design in its own right, though!

PS: Since when has a fin had to have a purpose, other than aesthetic, in old school sci-fi art?
