Preheat oven to 350 degrees F. For crust, in a bowl, combine crushed graham crackers, the 1/4 cup coconut, the 1/4 cup pecans, and the 2 tablespoons sugar. Stir in the 1/4 cup melted butter. Press mixture onto the bottom of an ungreased 9-inch springform pan. Bake for 10 minutes. Cool on a wire rack.
For filling, in a small heavy saucepan, cook and stir chocolate over low heat until melted; cool. In a mixing bowl, combine cream cheese, the 3/4 cup sugar, the sour cream, and the 2 teaspoons vanilla. Beat with an electric mixer on medium speed until combined. Beat in flour just until combined. Stir in eggs and melted chocolate. Pour over crust, spreading evenly.
Place springform pan in a shallow baking pan. Bake for 45 to 50 minutes or until a 2-inch area around the outside edge appears set and the center appears nearly set when gently shaken. Remove springform pan from baking pan. Cool cheesecake in pan on wire rack for 15 minutes. Using a small sharp knife, loosen edge of cheesecake from side of pan. Cool for 30 minutes. Remove side of pan; cool completely (about 1-1/4 hours).
Meanwhile, for topping, in a small saucepan, combine the 1/2 cup butter and the 1/4 cup sugar. Cook over medium heat, stirring to dissolve sugar. Remove from heat. Stir in the 1 cup coconut, the 1/2 cup toasted pecans, the milk, corn syrup, and the 1 teaspoon vanilla. Cool to room temperature.
Spread topping over cheesecake. Cover loosely and chill at least 4 hours.