I had this happen to me several years back. At the time, its a really catastrophic issue. Unless someone here gives you the name of a crack fixer, just resign yourself to needing a new block. The salvage yards in your area, this is true nationwide, (sorry Canada) have a network where you call one and they find you a new block no matter if they have to call several of their competitors to find it for you. Shop around, and each salvage yard will give you different prices depending on their business model. If you lived in central Kansas, I would sell you one pretty cheap. Even in Canada, don't pay more than a few hundred.
Fox, the problem isnt just that crack. If the engine was neglected to the point of having that crack, what else are you going to find, or worse, NOT find?