Comments:
Incredible vintage ad poster!
All (4) of these were actually my dream cars as a kid. Yes yes (2) Italian sports cars and (2) Swedish station wagons I know.
Spoilers at an angle to the slipstream creating down forces will increase Cd and related drag.
"Wet" surface area (skin friction) and all surface joins and gaps, eg doors, window frames and moveable covers, will increase Cd.