Preheat oven to 400°. Cut Pumpkin Spice Bread into 1/2-inch cubes with a serrated knife. Spread cubes in a single layer on a lightly greased jellyroll pan. Bake at 400° for 11 to 14 minutes or until lightly toasted. Remove cubes from oven; set aside. Reduce oven temperature to 350°.
Whisk together eggs, egg yolks, 1/2 cup sugar, pumpkin, lemon zest, and salt in a large mixing bowl until well blended. Whisk in milk and 1 1/2 cups whipping cream until blended.
Add toasted pumpkin bread cubes to custard mixture, stirring gently to moisten evenly. Let stand 20 minutes.
Grease an 11- x 7-inch baking dish. Pour bread pudding mixture into baking dish, spreading evenly; sprinkle with remaining 2 tablespoons sugar.
Pour hot tap water to a depth of 3/4 inch in a roasting pan. Place roasting pan in oven. Place baking dish containing bread pudding in center of roasting pan. Bake at 350° for 1 hour 10 minutes or until set at center. Let stand 10 minutes before serving. Serve warm with whipped cream or ice cream.