As long as young hearts endure, so will National Velvet and movies like it. in her star-making role, Elizabeth Taylor plays Velvet Brown, a wide-eyed adolescent who, assisted by her jockey pal (Mickey Rooney), trains Pie, a horse she won in a raffle, for the Grand National Steeplechase. Of course, no girl can ride in the National, can she? Yet Velvet, posing as a boy, assuredly does. Superbly directed by Clarence Brown, this exciting winner of two Academy Awards * (one to Anne Revere for her performance as Velvet's mother) costars a young Angela Lansbury and veteran Donald Crisp. The film has an off-screen postscript as winning as the on-screen finale: The studio gave Pie to Taylor after filming wrapped.