Ewing. J.R. Ewing. It doesn't have the same ring as 007's catchphrase, but speculating about who'll be cast as the sinister oil baron made infamous by Larry Hagman for the upcoming big-screen adaptation of the prime-time soap Dallas is Hollywood's favorite guessing game after who's in line to be the next James Bond. John Travolta is reportedly the J.R. front-runner, with Catherine Zeta-Jones and Matthew McConaughey possibly in line for wife Sue Ellen and brother Bobby. Original Lucy Ewing Charlene Tilton is pushing for a casting twist for her Lolita-esque character: ''Hire the Olsen twins. It's gonna take two people to fill my shoes.'' Screenwriter Robert Harling promises no such stunts, but don't expect a strictly faithful remake. ''We're starting from scratch,'' he says. ''We'll see the Ewing clan in 2006. Nothing is borrowed except an unbelievable dynasty on a ranch called Southfork that basically rules the world.'' So far his biggest hurdle is not getting trumped by current events. ''When dramatizing the antics of power-mad superrich Texans, you have to scramble to stay ahead of the headlines,'' he says. ''I come up with ideas and the next week it's in The New York Times.''