Obviously, it wouldn’t be possible to exactly design a modern car. But if you had all the aerodynamics, safety, and manufacturing knowledge from today - would it be possible to go to, say, 1970 and design a sedan body with swept-back headlights, a tapering roofline, flush-fit windows, a large crumple zone, and excellent space utilization? Would that body be able to be mass-produced in the factories of the era? What kind of drag coefficient could you achieve?
For reference:
1967 Citroen DS (swept-back headlights)
https://upload.wikimedia.org/wikipedia/commons/5/56/Festival_automobile_international_2011_-Vente_aux_ench%C3%A8res-Citro%C3%ABn_DS_21_Cabriolet-1969-_004.jpg
1967 NSU Ro80 (note the rounded corners and tapering greenhouse in the top view)
1967 BMC 1800 Berlina Aerodinamica (fastback profile)
1983 Audi 100 C3 (flush windows)
