Combine the corn syrup , butter, and brown sugar in a small saucepan and simmer until the sugar has melted. Pour this mixture over the bottom of a greased 9x13 inch casserole dish.
Place the bread slices over the sugar-butter mixture in the dish. In a bowl, beat together the eggs, milk, vanilla, and salt; pour this mixture over the bread. Cover the dish and let it stand in the refrigerator overnight.
The next morning, preheat oven to 350 degrees F (175 degrees C).
Uncover the pan and bake for 45 minutes. Serve while hot or warm or the French toast will harden in the pan. It can be reheated.