SANTA CLARA, Calif. -- Quarterbacks make their reputation on third down.Can they or can't they?Thursday night, Colin Kaepernick, under fire for leading a San Francisco 49ers offense that had scored a total of 10 points in its previous two games, was dominant on third down in a 35-11 victory at St. Louis.The 49ers relied on 153 rushing yards by Frank Gore. But Kaepernick added 167 yards through the air to supplement the offensive attack.