Combine raisins and rum in a small saucepan; bring to a boil. Remove from heat; cover and let stand at room temperature 1 hour. Drain raisins; discard rum. Finely chop raisins, and set aside.
Beat eggs in a large bowl at high speed of an electric mixer 3 minutes or until thick and pale. Gradually add sugar, beating until blended. Transfer mixture to a large saucepan; stir in milk. Cook over medium-low heat, stirring constantly, until mixture thickens and coats a metal spoon. Remove from heat, and let cool. Stir in whipping cream, vanilla, and raisins. Cover and chill thoroughly.
Pour mixture into freezer container of a 1-gallon hand-turned or electric freezer. Freeze according to manufacturer's instructions. Pack freezer with additional ice and rock salt, and let stand 1 hour before serving.