Preheat the oven to 350 degrees.
Crumble the dried white bread into a very large bowl.
Add the cooked white rice, and crushed saltines; set aside.
Cook the pork sausage in a large saute pan until it starts to brown. Add the celery and the onions; saute until the onions are transparent, 5-10 minutes.
Pour this over the bread and rice mixture.
Add the stock; mix well.
Add the salt, pepper, sage, and poultry seasoning. Mix well.
Reserve 2 tablespoons of the stuffing mixture for the Mushroom Giblet Gravy, (only if making Mushroom Giblet Gravy).
Pour the stuffing into a greased pan.
Bake until golden brown, about 45 minutes.