Cook macaroni according to package directions.

Prepare the cheese sauce.

Pour 3 cups of evaporated milk into a saucepan.

Supplement with 1 1/4 cups of water.

Add 5 heaping tablespoons of flour and stir until all lumps are gone.

Add salt and pepper to taste.

Place 1 stick of margarine in the saucepan.

Stir over medium-low heat until the sauce thickens.

Add chopped x-sharp Cheddar cheese to the sauce and stir until melted.

Add sliced American cheese and stir until melted.

Add sharp Cheddar cheese and stir until melted.

Combine the cooked macaroni with the cheese sauce.

Transfer to a baking dish.

Sprinkle bread crumbs over the top.

Bake in a preheated oven at 350°F (175°C) for 20-25 minutes, or until golden brown and bubbly.