I really hate to be the one to dash your dreams here, but if you are serious about that, I would have to say none of them. A 55g, if it is a 4 ft tank may possibly house 1 yellow tang (maybe...depending on rock and swimming room that is left), but I would advise against it. If you really want a tang, maybe a kole tang only, as they stay the smallest.
Ideally, I would recommend not getting a tang in your set up. There are a lot of other colorful fish out there that may appeal to you.