Unusual, dynamic model-turned-actress who followed her film debut in John Huston's "Fat City" (1972) with a memorable, Oscar-nominated performance in George Lucas's seminal coming-of-age film, "American Graffiti" (1973). Clark's subsequent career, however, has not lived up to her fine work of the 1970s in such films as "The Man Who Fell to Earth" (1976) and "When You Coming Back, Red Ryder?" (1978) and her country turns in the TV films, "Amateur Night at the Dixie Bar and Grill" (1979) and "Rodeo Girl" (1980). She has appeared mostly in fairly obscure or routine genre fare, from "National