Preheat oven to 350°. Grease and flour a 15x10x1 inch jelly roll pan. Combine sugar, oil, pumpkin and eggs. Beat on high for 1 minute. Add cake mix and pumpkin pie spice. Mix 2 minutes on high speed. Fold in nuts, if desired.

Pour into the pan and bake 25-35 minutes or until a toothpick inserted in the center comes out clean.

Combine the frosting and cream cheese until smooth. Frost cooled bars. Store in the refrigerator.