The other cars in the group do and, even if it's not authentic, if you have night races I think they should make them work.
No I'm against being inauthentic. If there are variants of the car in real life that have headlights then OK, but just because you can race at night isn't a good argument. Not every series is meant to be raced at night.
If you are talking about the beetle, it doesn't have headlights, even though some other cars in the same class have. I agree with Gevatter that it should stay authentic. If not, the next thing would be an F1 car with headlights....
The Copa Classic cars do run 12h races, so should be equipped with highbeams. Although the Fuscas in particular seem to use external lights mounted on top of the bonnet:
