The San Francisco 49ers, one of the more aggressive teams this offseason in terms of acquisitions, enter this weekend's draft with a league-high eight picks in the first four rounds: one first-round selection, a second, two thirds and four fourths. On the eve of the draft, the Niners already were poised to maximize the value of one of those fourth-round picks. According to league sources, San Francisco and division rival Seattle are working toward a trade that would send Seahawks wide receiver Darrell Jackson to the Niners in exchange for one of their fourth-rounders, believed to be the Niners' third selection in the round, No. 124 overall. The New Orleans Saints and Tennessee Titans, whose new general manager Mike Reinfeldt came over from Seattle, are also believed to be talking with Seattle about Jackson.