That last one's gorgeous. I'd like a 1:43 model of it!
You could probably mount some NACA inlets on the C pillar area of the boat tail and duct air past the cooling outlets, finally exiting the rear of the tail. The air moving through the ducts and into the wake would suck the cooling air right out, and probably not add too much drag- especially when compared to not having an upper part.
Actually, put the inlets up top like an RS200 (but of course use NACA ducts):
This is the one I'd choose, but it might be worth the effort of smoothing out those interior corners that develop between the rear fenders and the body sides. Think about building a custom rear bumper?
It would be neat to find a ratty Bug body , hack it off where your boat tail begins, and build a new rear end with perfect curvature.
Last thing.
If you're doing this version, use some '63 Thunderbird taillights to make it look like a rocket ship. And add NASA logos to the side
