For crust, in a medium mixing bowl combine flour and salt. Cut in shortening until pieces are the size of small peas. Stir in the 1/3 cup pecans. Sprinkle 1 tablespoon of the water over part of flour mixture, gently tossing with a fork. Push to the side of the bowl. Repeat with remaining water until all is moistened. Form dough into a ball. On a lightly floured surface, flatten dough with hands. Roll dough from center to edges, forming a circle about 15 inches in diameter.
Fold pastry into quarters and transfer to a 12- or 13-inch pizza pan. Unfold pastry and ease into pan. Trim pastry to 1/2 inch beyond edge of pan. Fold under pastry and flute edges. Prick pastry with a fork. Bake in a 425 degree F oven for 12 to 15 minutes or until golden. Cool.
Meanwhile, for filling, in a heavy medium saucepan stir together sugar and cornstarch or flour. Gradually stir in milk. Cook and stir over medium heat until thickened and bubbly. Cook and stir 2 minutes more. Remove from heat.
Gradually stir about 1 cup of the hot mixture into egg yolks. Return all egg yolk mixture to saucepan. Cook and stir until mixture begins to bubble. Reduce heat. Cook and stir for 2 minutes more. Remove from heat. Stir in butter or margarine and vanilla. Cover surface with plastic wrap. Cool to room temperature. (Do not stir.)
Spread peach or apricot preserves on cooled pastry. Spread filling on top of preserves. Cover with plastic wrap. Chill for 4 to 24 hours. Just before serving, arrange peach slices on top of filling. Sprinkle with the 1/4 cup pecans or coconut. Makes 16 servings.