best body for road race setup

That's funny Steve, I was going to post the opposite. The reason is that the fastbacks have better weight distrubution and are more rigid to begin with. But you're point is very valid. So there's the pros and the cons. I think the final decision depends a lot on the class and type of racing.
The earlier As are about as light of a starting point as you can get. On the other hand, some of the E and Bs will get track width (which as fundemental of physics) and potential for better aero.