Spray a 9-by-13-inch ceramic or glass baking dish with olive oil spray. Slice bread into 1-inch pieces; place in baking dish.
In a medium bowl, beat eggs and egg whites. Mix in pureed squash, milk, vanilla extract, brown sugar, pumpkin pie spice, 1 ½ teaspoons cinnamon, and nutmeg. Crush ½ cup pecans and mix into squash mixture, along with raisins.
Pour mixture over bread pieces, making sure all pieces are covered.
Seal tightly with saran wrap and place in fridge overnight.
When ready to bake, preheat oven to 350° Fahrenheit.
Remove saran wrap; crush remaining pecans, and top evenly over mixture.
In a small bowl, combine granulated sugar with remaining cinnamon. Sprinkle evenly over mixture.
Bake for 30-35 minutes, until batter is firm. Serve with maple syrup, if desired.