Glen,
Great question and I bet some of our members will have some good information.
For precise answer, I wonder if it also depends on what exact model of Cobra we are talking about… 289 or 427, with or without hood scoop or
oil cooler scoop, so forth and so on.
Then compare that to what Peter Brock did to streamline that 'brick' … what's the co-efficient of drag for a Daytona Coupe ?