This episode's headline: Used Car Rule. The guests include PATRICIA BAILEY, Federal Trade Commission; GEORGE LYLES, National Automobile Dealers Association; Sen. JOHN DANFORTH, Republican, Missouri; Sen. LARRY PRESSLER, Republican, South Dakota. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: CHARLAYNE HUNTER-GAULT, Correspondent; LEWIS SILVERMAN, Producer; PEGGY ROBINSON, Reporter