Welding cast iron often generates more problems than it fixes, unless you have competent professionals do it, and they charge for it. Call a diesel repair shop and get an estimate. Not some back alley hatchet shop either, a decent Cummins/Cat/Inland Diesel etc shop.

Like I said, get it brazed, generally a phosphor bronze process, it'll be plenty strong and won't have a bunch of hardness/induced stress issues like if someone hacked at arc welding it with nickel rod. S/F....Ken M