Preheat oven to 350. Grease and flour a large Bundt pan and set aside. In a small bowl combine brown sugar, cocoa, cinnamon, raisins and nuts. Set aside .
In large mixing bowl, cream together margarine and sugar. Add vanilla and eggs, mixing to blend.
In a separate bowl, sift together flour, baking soda, baking powder and salt. Add dry ingredients to the large mixing bowl. Mix well. Add sour cream and mix to blend.
By hand, fold in brown sugar-nut mixture. Pour batter into prepared Bundt pan and bake in 350 oven for 50-60 minutes, until done.