Try putting the headlights in pods, mounted on aerodynamic stalks. I think that would minimize the disturbance to the flow over the vehicle itself.
It's actually practical because the vehicle can use off the shelf projector headlights like these
Low beam
http://www.rallylights.com/detail.aspx?ID=1800
High beam
http://www.rallylights.com/detail.aspx?ID=1801