Preheat the oven to 350 degrees F. Combine the flour, oats, 1 1/2 cups brown sugar, baking soda, 1 1/2 teaspoons cinnamon and 3/4 teaspoon salt in a large mixing bowl. Melt 3/4 cup butter, let it cool, and pour into the mixing bowl with the dry ingredients. Stir until a soft dough forms. It should be just slightly crumbly. If the dough feels wet and heavy, add a little more flour.
Line the bottom and sides of a 9x13 inch baking dish with Reynolds Wrap(R) Aluminum Foil. Press 3/4 of the dough into the dish. Reserve the remaining 1/4 to use for topping. Bake for about 10 minutes or until the top is barely golden brown.
Combine the pumpkin, evaporated milk, eggs, white sugar, 1 teaspoon cinnamon, 1/2 teaspoon salt, ginger and cloves and mix until blended completely. When the crust is done, pour the filling mixture over the crust and continue to bake for 20 minutes.
Remove pan from oven and sprinkle the reserved dough over the filling. Bake for another 20 minutes. Let the bars cool.
For the caramel sauce, melt 4 tablespoons butter, 1/3 cup brown sugar and 1/3 cup cream together in a small saucepan. Set the temperature on medium heat and stir constantly until the caramel is smooth and barely bubbling. Pour over the bars. Cut and serve!