Spray a 9x13 inch baking dish with cooking spray. Place bread in the prepared baking dish. In a large bowl, combine eggs, pumpkin, sweetened condensed milk, Adams cinnamon, Adams allspice and salt. Stir with a whisk until fully combined. Pour egg mixture over the bread, gently pressing down the bread to ensure each piece is soaked. Cover with foil and place in the refrigerator for at least 4 hours, or overnight. Preheat the oven to 350 degrees. Remove the baking dish from the refrigerator, remove the foil and sprinkle the topping evenly over the top. bake for 40 minutes uncovered, then cover with foil and continue to bake for 10-15 more minutes. Allow the casserole to cool slightly, top with powdered sugar and serve with maple syrup.