I have found some of the old Harrison heaters, 47-53 at swap meets, most of the time for under $20 or so. It's a risk but at least you get the heater core. Checked at an older radiator shop in Ft Worth, the old man knew what I was talking about(the round core) said no charge for checking for leaks, and about $35 for a repair job. Something to keep in mind rather than spending big bucks for a repo core.
