I use plain old .030 steel wire. Years ago I broke off one of the stud flanges on Nova's manifold and was in college (which means I was broke

)Couldn't afford new one so I broke out the welder. It was just a little 90amp century welder cranked up all the way. worked like a charm. I also rigged up both cylinder heads on my old 400 that cracked around the steam holes. They say necessity is the mother of all invention. Ha! More like you broke it while street racing and better fix it before your dad finds out, or your goose is cooked!
I don't know the proper way to fix cast but I know what worked for me in a pinch. Now I'm alittle more financially stable so I'm able to just chuck em and replace em.