Something big! I think you're taking off a pretty big fairing so you have to replace it with something fairly big to keep the look of the bike balanced. If you use small lights it looks like there's something missing. If you're thinking of selling the bike in the future you should keep the original fairing. There was a factory "café racer" 400 on here a while back. It had a large single head light and it looked good. Someone might be able to find the pictures of it.