I'm going with .27 - I would have gone lower, but Kach pointed out the open grille.
As far as the open wheel wells, and lack of side skirts, I keep thinking back to the HotRod 1980 Camaro, which achieved a verified .201 Cd with nothing more than an airdam, a plugged grille and headlight assembly, a simple shelf spoiler, lowering, and moon disks.
No side skirts, no belly pan ( later added, but not present early on when tested ) etc.
( And that .201 figure is
with the giant scoop on the hood !
Amazing.