Southern 7-Up Cake

1 (18.25 ounce) box yellow or pineapple cake mix
4 eggs
1 small box vanilla instant pudding
3/4 cup vegetable oil
1 (12 ounce) can 7-Up, at room temperature

Beat all ingredients together well for 2 minutes with electric mixer. Pour batter into 3 (8-inch) layer pans or a 15 x 10-inch jellyroll pan that has been greased and floured. Bake at 325 degrees F for 25 to 30 minutes. Cool for 10 minutes, if in layer pans, and remove from pans to cool thoroughly on wire rack. Fill and frost.

Filling:
1 cup granulated sugar
1 heaping teaspoon cornstarch
4 eggs
1/2 cup margarine
1 (No. 2) can crushed pineapple
1 1/2 cups flaked coconut
1 teaspoon vanilla extract
1 cup coarsely broken pecans

Combine first 6 ingredients and cook over medium heat until thick. Remove from heat and add vanilla extract and pecans. Cool before spreading between layers and over cake. If using a 15 x 10-inch pan, leave cake in pan and spread frosting over top.