I don't see why you should worry about that... And about the aesthetics - the original look is far more better than anything else, that can be done. With closed or opened headlights - this car will look MUCH better than if you fit any kind of conversion headlights... Better give these money for something more important about the car (my opinion).
And now, when I think about it - I've actually never seen a conversion headlight kit for the F355. Maybe because the market for it will be too small.