best body for road race setup

I'd avoid the pure fastback profile cars (Barracuda fastbacks and Dusters). They create lift in the rear at speed. A sedan profile with some flat deck in the back creates downforce.

Think about when nascar had the Thunderbirds kicking butt with Bill Elliot and then GM made those Aero Coupes. GM added the slanted rear window, but kept and short flat deck on the end. The T-birds had a similar thing already.

I like the 67-69 Barracuda Coupe because they have a rounded front nose and a flat rear deck. But the rear is sort of long. And it's a bummer the rear window is sunk in at the top.

I think 63-65 Valiants have promise because they are lighter and smaller packages.

....Nothing is perfect.