Id pretty much do as Rob said previously, Id go with high nickel rods using a stick welder. On a piece like yours I wouldn't pin it, I feel that is more likely to weaken it rather than strengthen. A reasonable weld should be plenty strong enough . I have found that the cast iron on some old machines seems to be of lower quality that modern castings and welding can be difficult but you wont know that until you try. Gave one piece off a 1930's ? bandsaw to a mate who is an experienced boilermaker and he struggled.
Nickel rods give a nice ductile (pliable) deposit so cracking shouldn't be a problem on a simple piece like yours. If you where welding a wheel where expansion in one place creates stress in the whole casting then much more care needs to be taken with even pre heating of the whole casting and very gentle cooling. My old tafe teacher said that burying a welded casting in cement powder is a good way to cool it slowly, but shouldn't be necessary in your case. That said, a bit of pre-heating cant do any harm. Prepare it well and if you dont get full penetration, turn it over and vee it out then fill that in.
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