You're correct the 1966 Lotus Europa had a similar profile to the R380, just as the aforementioned Porsche 906 above in the post. It was a style at the time in terms of aerodynamics. Will include some comparison pics below of other race cars from the same time period and you can see see how similar in design they are to the Prince.
1966 Lotus Europa

1966 Porsche 906

1966 Ferrari 330 P3
