The problem is that the gasket is now compromised and the manifold is also probably warped. To do this job right, the manifold has to be removed and then resurfaced and new gaskets installed. In that process several more studs will likely break. The problem is that the cast iron manifold is so long that it moves quite a lot during heat cycles (expand and contract) and the cheap studs Ford installed can't take the movement so they break. That is also why many go to headers instead if the cast iron manifolds. You can achieve some measure of longevity to your repair job by installing stainless steel studs and nuts and using a good antisieze compound. It is not a quick job and it can get expensive to have a mechanic (or machinist) do the work.
Sorry for the bad news from someone who has been there.
