Copper vs Aluminum heater core for 71 valiant

All of the old cores were brass or copper/ combo of. Aluminum did not come into play until......?? the nineties ? or so

Even so, the old cores can rot out depending on water quality. Back when I was stationed in San Diego, the water down there would rot a radiator out in a few years. That is where I learned to use store bought purified water in a rad.