Beat butter at medium speed with an electric mixer until creamy; gradually add 1 1/2 cups sugar, beating well. Add eggs, 1 at a time, beating until blended after each addition.
Combine flour and next 6 ingredients in a large bowl; add to butter mixture alternately with pumpkin, beginning and ending with flour mixture. Stir in raisins and vanilla.
Spread batter into a greased and floured 13" x 9" pan; sprinkle with Pistachio Topping. Bake at 350° for 45 to 50 minutes or until a wooden pick inserted in center comes out clean. Cool on a wire rack.
Beat cream cheese, powdered sugar, and milk in a small bowl until smooth, using a wire whisk. Using whisk, drizzle cream cheese mixture over cake.