BIRMINGHAM, Ala. — South Carolina and LSU have two major new challengers for Southeastern Conference supremacy. The programs that have combined for the past three national championships are joined by two other preseason Top 10 teams, SEC newbies in fourth-ranked Texas and 10th-ranked Oklahoma. But the top-ranked Gamecocks are going for their third national title in four years — minus departed star Kamilla Cardoso — after romping through a 38-0 season.