I've been thinking on this a bit. I think that studying southpaws fighting inside is counter-productive. Generally it is a bad spot for a leftie to be as he loses the advantages of angles. Like LaMotta said, in close they are all the same. Even southpaws like Andy ganigan- who liked to get close and fight- weren't inside fighters. He did his damage coming in, more than inside.
Maybe Chiquita (Humberto) Gonzalez. He fought mostly southpaw and liked to fight in close. For style points, Georgie benton, Emile griffith. Sandy Saddler and Little Red Lopez were tall guys that could fight in close, and Saddler knew all the tricks. The Charles Williams v James Toney fight was fought real close.
watch for things guys do at that range. How you can pull/push his glove aside to land a punch. chavez used to do this- hit a guy's right elbow with his left glove to mis-direct a punch.