Beat yolks w/fork in medium bowl. Mix sugar, cornstarch and salt in 2 quart saucepan. Gradually stir in milk. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 2 minutes.

Immediately stir half hot mix slowly into yolks, then back into mix left in pan. Boil and stir 1 minute, remove from heat. Stir in margarine, vanilla, and 3/4 cup coconut. Pour into shell. Press wrap onto filling. Refrigerate about 2 hours or until set.

Top with whip cream (and opt. coconut) before serving.