perhaps another car worth mentioning is the opel kadett.
in 1979 the kadett D came out. at the time a mechanically advaced car with clever practical package and a, for the time, class leading Cd of 0.39 (!)
in 1984 the next gen of this car basically placed an aerodynamic body, on the same mechanical underpinning
yet the Cd went to 0.32
and even 0.30 for the GSI
(rear spoiler, hood vents, different bumper and grille shape with lower airdams in front of the wheels and plastic moldings shielding the front face of the rear tires )
i think this mostly shows the importance of detail optimisation, as both cars have esentially the same layout.