I know that we've had some discussion LED'* in the past. Some like 'em, most do not. Look at this thread and you'll get Zzzekes opinion.
If your lights are bright now, be prepared for a big dissapointment with most LED'*. You'll also need to change to a thermal flasher or add resistance to the socket that contains the LED'*. As far as legality goes, just don't cross the New Jersey state line. I can't speak for the other 49 states or our friends up in Canada.