Allow eggs to stand at room temperature for 30 minutes. Meanwhile, grease and flour a 10-inch fluted tube pan; set aside. In a medium bowl stir together flour, baking soda, cinnamon, nutmeg, salt, and cloves. In a small bowl combine pumpkin and milk. Set bowls aside.
Preheat oven to 350 degrees F. In an extra-large mixing bowl beat eggs, granulated sugar, brown sugar, 3/4 cup shortening, and vanilla with an electric mixer on medium speed for 2 minutes, scraping sides of bowl occasionally. Alternately add flour mixture and pumpkin mixture to egg mixture, beating on low speed after each addition just until combined. Divide batter in half.
In a small microwave-safe bowl microwave 1 cup of the chocolate pieces on 100 percent power (high) for 1 to 2 minutes or until melted, stirring every 30 seconds. Stir melted chocolate into one-half of the batter. Spoon half of the plain pumpkin batter into the prepared pan. Gently spoon the chocolate batter over pumpkin batter in pan. Top with the remaining plain pumpkin batter. Using a table knife, swirl batters together to marble.
Bake for 50 to 60 minutes or until a wooden toothpick inserted near the center comes out clean. If necessary to prevent overbrowning, cover cake loosely with foil for the last 10 minutes of baking. Cool cake in pan on a wire rack for 10 minutes. Remove cake from pan; cool completely on wire rack.
In a small microwave-safe bowl microwave the remaining 1/2 cup chocolate pieces and 1-1/2 teaspoons shortening on 100 percent power (high) for 1 to 2 minutes or until melted, stirring every 30 seconds. Drizzle melted chocolate over cake.