‘70 Dodge Dart 318 Stock Intake Problem

I would first try to back it out using long nosed pliers on the part viable from inside the water passage. You could also use a drill that is larger than the ID of the brass but smaller than the OD of the cast iron threads to thin the brass and then using a punch or even a small screw driver between the cast iron and the brass try to bend the brass in on its self away from the cast iron. Good luck.