I have a B engine where the slinger has been ground off. It now relies on a neoprene or nitrile seal which is less than wonderful. I'm planning on replacing the slinger by pouring one insitu using Babbit, then turning it to size. I don't like the idea of building one up with weld. The babbit doesn't require near as much heat so should be OK if a little fragile. Once in place, it will be fine.
Just an idea to consider.