... Please post the aero info for the old classic cars and hot rods if you find it...
The only thing that comes to my mind, is an article one of the engineer-editors (Don Franciso maybe?) wrote in Hot Rod back in '53 or '54 (need to dig it out sometime). He showed a short list of "representative" vehicle types with ballpark drag coefficients. The only one I recall was drop-tank lakesters, at about 0.9 Cd.