Huck's way of escape is certainly possible, but far more difficult in this modern age. Today, it's almost impossible to simply "disappear". Children just don't show up in towns where they don't belong. Families know what their relatives look like.... how they've changed.... think Facebook. Huck's leaving would have caused a far greater stir, as today multiple towns would have been involved in the search, not to mention the technology that would have determined there were living bodies on the island. Thus, it might sound like fun, but I doubt anyone would get very far. All in all, I'd never say never, but it's a long shot.