I have one that leaks out of my 74 Ramcharger (440 A/C truck)

the 72-80 truck heater core's for factory A/C trucks have been out of production for 6 or 7 years best I can tell. I had to buy a used one and have a local radiator shop soldier up some cracks. The one that came out of my truck appears to have had water in it and froze. It looked like an aquarium aerator when submerged and filled with air.