Slant 6 Turbo 68Dart Project

It is not uncommon to find wires like that inside head and block castings. My understanding is that they were used to hold the sand cores together when the block was cast, and after cast the sand is removed but the wire remains, or something to that effect.

Have you had the rad flushed / checked? "look"at the core with a infrared temp probe to see if it is hot and progressively cools, or if it appears that the coolant doesn't flow through portions of it due to being plugged up.