Heather Thomas who once rivaled Farrah Fawcett and Heather Locklear as TV's top pinup girl is back, but this time she's taking on a new Hollywood role: Hip Screenwriter of the Moment. Following a three-studio bidding war, the former Fall Guy star got a mid-six-figure deal from Touchstone for her first screenplay, School Slut, a '70s-era dark comedy described as a cross between Welcome to the Dollhouse and Heathers (of course). ''I wanted to explore the stringent rules of high school because I have two daughters,'' says Thomas, 39. And yes, she knows what you're thinking. ''It's like, 'Oh! She can walk and chew gum!''' says the actress, who's also developing a youth-oriented TV series. ''But nobody knows I've been writing all along, taking classes, and worshiping at the feet of the writing gods.'' Think those higher powers could persuade Lee Majors to play the rough-and-tumble principal?