Doug, mine was like yours. The P.O. had disconnected the heater hoses. Turned out my core was fine, it was the control valve that was bad and leaking.
I tested my heater core using a section cut out of a bicycle tube. Leaving the valve stem in and clamping the tube around the core pipes. Then submerged it in a tub of water and added air pressure to the tube.
No bubbles from the core, but the valve was leaking bad.
