Tom Selleck's CBS series, Magnum, P.I., which has been pitted against NBC's top-ranked Cosby Show for two seasons, is having more than ratings trouble: Magnum's producers are three episodes short of what the network wanted this season. Bad weather in Hawaii and script delays are blamed. Shooting comes to a halt next week because Selleck committed himself to work only six months on this season's episodes. Plans to shoot next fall's two-hour opening episode in Hong Kong have been scrapped because CBS balked at the budget. All of this could lead to a shake-up of the production staff, with the show's co-creator and executive producer Don Bellisario taking the heat. Selleck, who's renegotiating his contract, has agreed to a longer shooting schedule next season.

Jane Fonda won't be surprised when she reads about herself in ex-husband Roger Vadim's kiss-and-tell autobiography, imaginatively titled Bardot, Deneuve, Fonda, which is due out next month. Vadim says he showed Fonda the sections about her before publication. "We made a few changes, where I had made a mistake or she felt I should explain more," says Vadim, who claims in the book that he was impotent early in his relationship with Fonda. "She made suggestions that were good for the book. We were in agreement on everything." Vadim didn't give his other past loves, Brigitte Bardot and Catherine Deneuve, a sneak peak at his prose. "Everything I said is flattering, pleasant, amusing and good for their image," contends Vadim. Besides, he adds, "They don't read English."

Word is Eddie Murphy has agreed to do Beverly Hills Cop II for a salary of $8 million and an undisclosed percentage of the gross, with an additional $4 million going to his production company....

Teen-movie meister John Hughes, whose credits include Pretty in Pink, Breakfast Club, Weird Science and Sixteen Candles, is finally graduating from high school. In his next film, Some Kind of Wonderful, the female lead will be a college senior who's in love with a frosh. No cast yet, but varsity brat packers are likely to be recruited....

Sophia Loren will star in a CBS movie called Mother Courage, which is based on the true story of a drug addict's mother who helped break a $3.5 billion cocaine ring....

Charlene Tilton, whose character Lucy Ewing was dumped from Dallas, may reappear in the role to join the rest of the Ewing clan on Knots Landing next fall....

NBC is developing a movie based on Roe vs. Wade, the landmark Supreme Court case that resulted in legalized abortion....

Pop singer Jennifer (Up Where We Belong) Warnes is recording an album of Leonard Cohen songs, including Bird on the Wire and Suzanne, for release this summer....

Wearing a blond hairpiece wasn't the toughest assignment for Robert Duvall in Hotel Colonial, a movie co-starring John Savage and Rachel Ward due out this fall. Playing a South American drug kingpin, Duvall tangles with a giant anaconda in the jungle. He agreed to do the scene only after the director, Cinzia Torrini, allowed the snake to be draped around her first. Gripes Duvall, "Not only did I have to fight a 16-foot anaconda, but the director insisted I had to act like I was winning."