Heat oven to 350°F. Grease and flour 10-inch tube or 12-cup fluted tube cake pan. In large bowl, combine cake mix, 3/4 cup milk, 1/2 cup margarine and eggs; beat at low speed until moistened. Beat 2 minutes at high speed. Stir in 1/4 cup coconut and 1/4 cup nuts. With spoon, marble chocolate through batter. Pour half of batter (about 2 cups) into greased and floured pan.