Kenworth K100 Heater Core?

Of course, my truck having lived most of its life in Georgia and Florida, the heater core is shot. Took me a while to figure out the right combination on the mess of valves (half of which leak when open, so they're all coming out) heading into and out of it, but once I did, I found it was not only plugged, but also leaks well enough to cover my passenger windshield in coolant.

I poked my head around online, and can't find anything about this heater core. No part number, no vendors, no nothing.

Does anyone know of any part numbers/interchangeable units? I can rig something up if these heater corea are extinct, since the mount is easy enough to get to, and I can modify the heater box easily, since I can't have riders anyway.

Were these heater cores worth anything to begin with? Any known issues with them?

Thanks to anyone willing to offer some input.

1979 Kenworth K100
VIN- 275680K

I measured mine, and it came out to 2.5"X8.5"X15.5", but it doesn't look like there are any part numbers or manufacturer info on it anywhere. Looks like its been repaired at least twice, but this leak appears to be coming from the middle of the core, with all the repairs along the ends and on the tanks.