Yeah Bennie, what meant was to find a copper alloy heater core with brass tubes to solder to. I found one years ago & it's stashed away for the day I finally need it.
My old radiator go to shop, Associated Radiator in Covina CA had brass radiator & heater cores on hand for repairs last time I asked about it a year ago.
https://associatedautorepair.com/
https://usradiator.com/cores