Combine strawberries and 1 cup granulated sugar in a large bowl, tossing gently to coat. Let stand at room temperature 1 hour; toss gently. Cover and chill 1 to 2 hours.
Meanwhile, combine flour and next 4 ingredients in a large bowl; cut in 3/4 cup butter with a pastry blender until mixture is crumbly. Add milk, stirring with a fork just until flour is moistened. Turn dough out onto a lightly floured surface, and knead 4 or 5 times.
Roll dough into a 12-inch square. Combine brown sugar and 2 tablespoons melted butter; sprinkle over dough, patting gently with fingers. Sprinkle with pecans. Roll up, jellyroll fashion; pinch seams and ends to seal. Cut roll into 12 (1-inch) slices. Place slices, 1 1/2 inches apart, on a lightly greased baking sheet. Bake at 425º for 15 minutes or until lightly browned. Remove pinwheels from oven, and cool on wire racks.
Beat whipping cream at medium speed with an electric mixer until foamy; gradually add powdered sugar, beating until soft peaks form.
Place 1 pinwheel on each serving plate; spoon strawberry mixture over pinwheels. Dollop shortcakes with whipped cream.