A trio of former Metropolitan Talent Agency agents have joined colleagues Jeffrey Benson, Dianne Fraser, Stephen Rose and Richard Weston in their newly launched literary agency, which opens its doors April 5 at the Fox Plaza in Century City.The three are Mark R. Harris, Stephen Marks and David McIlvain. About two weeks ago, former MTA partners Benson and Weston dissolved their partnership with Christopher Barrett at his request and re-formed the Major Clients Agency banner they originated in 1985. In 1990, Major Clients merged with the other principals of MTA. Harris brings with him to Major Clients two-time Emmy-winning writer Paul Haggis (“thirtysomething,”"City”), Mark Ganzel (writer/producer “Coach,” co-creator/producer “Fresno,”"Popcorn Kid” and “Princesses”); IRS Media TV; Cherry Lane Music Publishing Co.; and Premiere Films, among others. Harris, who at MTA was involved in the packaging of such shows as “City” and “America’s Funniest Home Videos,” joined the agency in January. Marks, a TV packaging agent who joined MTA eight months ago after 6 1/2 years at ICM, brings clients John Conboy, Bob Jaffe, Buddy Sheffield, Gary Pudney, Paul Flattery, Jim Yukich and Sun International Pictures, among others. He is credited with helping package such shows as “Cops,”"Roundhouse,”"Name Your Adventure,”"What Happened,”"Getting Over” and “Yearbook.” Clients joining McIlvain at Major Clients include writer/actor Dean Cain, who is set to star as Clark Kent in the upcoming ABC/Lorimar TV series “Lois & Clark: The New Adventures of Superman”; and director Christian DuGuay, whose credits include New Line’s “Live Wire.” McIlvain joined MTA last October from Innovative Artists Agency.