Those are called carb expansion plugs. Guess from when the carb body was cast. I'd try to tap with a drift pin (Flat punch slightly smaller than plug). When installed they are slightly convex and the drift pin flattens them out to fill the hole. Wonder if JB Weld would stick and seal (clean well first)?
I once "fixed" a pin hole in the fuel tank of a type I with JB Weld.