Preheat the oven to 350°F (177°C). Thoroughly grease and flour three loaf pans, or line each pan with parchment paper to help the finished loaves release cleanly.
Place the pumpkin purée, room-temperature eggs, olive oil or melted unsalted butter, and water in a large mixing bowl. Whisk vigorously until the ingredients form a smooth, uniform mixture.
In a separate bowl, combine the sifted flour, baking soda, granulated sugar, salt, cinnamon, nutmeg, and allspice. Stir until the spices and leavening are evenly dispersed.
Add the golden raisins and chopped walnuts to the dry ingredients, when using. Toss gently so they are distributed throughout the flour mixture.
Gradually add the dry mixture to the bowl containing the pumpkin mixture. Stir only until the batter is evenly blended and no visible pockets of dry flour remain.
Distribute the batter evenly among the three prepared loaf pans. If desired, scatter roasted pumpkin seeds or old-fashioned oats over the surface of each loaf for added texture.
Place the pans in the preheated oven and bake for approximately 1 hour. The bread is ready when a toothpick inserted into the center of a loaf comes out clean. Baking time may vary slightly according to the oven and the dimensions of the pans.
Transfer the baked loaves to a wire cooling rack. Allow them to rest in their pans for 10–30 minutes, then carefully remove them and return them to the rack.
Cool the pumpkin bread completely before slicing. Full cooling allows the interior crumb to set properly and helps produce cleaner, more even slices.