Toss raisins with 2 tablespoons flour; set aside. In a large mixing bowl, combine the brown sugar, baking powder, cinnamon, baking soda, salt and remaining flour. Add oil and eggs; beat well. Stir in carrots and reserved raisins.
Transfer to a greased 13-in. x 9-in. x 2-in. baking dish. Bake at 325° for 55-60 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.
For frosting, in a large mixing bowl, beat cream cheese and butter until smooth. Beat in orange juice and vanilla. Gradually add confectioners' sugar; beat until light and fluffy. Spread over cake. Store in the refrigerator.