Once long ago I repaired a pot metal part on a classic car just as a challenge
using my then new Hobart TIG welder. It wasn't easy, took quite a while, and
was totally cost ineffective. So the short answer is, get a new part if you
can, it's cheaper.
The problem with welding pot metal is the sharp melting point of the pure zinc
castings and the lack of an oxide coating that will support the molten weld
until it cools. At the time I experimented with this technique, only pure zinc
welding filler rod was available. Maybe somewhere there is better system now.