Combine flour, baking soda, cinnamon and salt in a small bowl.
In a measuring cup, stir together milk and lemon juice (mixture will appear curdled).
Beat sugar, pumpkin, eggs, brown sugar and vegetable oil together in a large bowl until combined. Add in pineapple, carrots and milk mixture and mix until combined.
Gradually add in the flour mixture.
Fold in 1 cup of walnut and coconut.
Pour into 2 greased, 9 inch cake pans.
Bake in preheated 350 degree oven for 30-35 minutes or until a cake tested inserted into the center comes out clean.
Cool in pans for 15 minutes.
Remove to cool racks and cool completely.
To make cream cheese frosting, beat cream cheese and butter in a large mixing bowl.
Gradually beat in powdered sugar.
Stir in orange juice and vanilla.
To assemble cake, frost between layered, on top and sides of cake with Cream Cheese Frosting. Garnish with remaining walnuts.
Store in refrigerator.