Grease a 9 x 13 pan, and preheat oven to 350 degrees F (175 degrees C).
Combine cake mix, pudding mix, slightly beaten eggs, and vegetable oil in a mixing bowl. Beat on medium speed until batter is light and fluffy. Add 7-UP ™ , and beat in well. Pour batter into prepared pan.
Bake for 35 to 40 minutes, or till done. While cake is baking, prepare the topping; it will take about 15 minutes to prepare.
In a medium non-aluminum saucepan, combine sugar and flour. Stir in 3 eggs yolks, butter or margarine, and pineapple. Cook over low heat, stirring constantly, until thickened. Remove from heat, and stir in coconut. Spread topping over warm cake.