Ditto what Apogee said. Something too heavy has been attached to the top link, probably repeatedly. The cracks in the top housing probably stop at the bolt hole radius as it would normally stop propagation of the crack. The bottom housing though????
Even welded it will probably not be as strong in tension as the original casting. Some additional reinforcing bracket to take some of the load might be a good idea. Specialty rods for cast are much better than they used to be, but still need some experience to use correctly.
It can not be welded with a mild steel rod as was suggested earlier. The Item compared to was an over the road differential, those are normally cast steel not cast iron like your case (easy to mix up, can look a lot alike).
To do it right you'll at least have to take the top case unit off.
Good luck!