I've had the same issue with my 4.7 liter. The first time I replaced just the gasket and all the bolts. A few years later it happened again and I replaced the manifold and gasket with all bolts. The rear bolts that hold on the manifold are known to snap off. They had issues with the manifolds warping causing the bolts to snap. I'd recommend replacing the manifold. It's a little bit of work can be done with basic tools. It helps to take off the tire and plastic inner fender well to gain access to some of the bolts.