A good welder could "V" the required weld area and weld it back together. The weld would be into the threads requiring it to be tapped out. Al does weld well, but that said I would be more inclined to swap the internals into a good case. The time required is minimal, like an hour. Then the cost of a good used housing. Seals and most gaskets should be reusable as it has not run. The issue with welding your case is, what if it let's go again driving down the road. If that happens you need another case and likely total rebuild on that one.
