Justin Thomas of Goshen, Ky., overtook leader Denny McCarthy of Burtonsville with a birdie on the 17th hole, and after finishing regulation play all square, won the ensuing first extra hole with a par to gain the final of the U.S. Junior Amateur championship in Ada, Mich. McCarthy had advanced to the afternoon match when he birdied the first playoff hole to defeat Canadian Richard Jung in a morning quarterfinal. pairing. Thomas will face Jim Lio of Smithtown, N.Y., , a 3-and-2 winner over Robby Shelton of Winner, Ala., in a scheduled 36-hole final. Indoor football