Radiator leak at top seam

That is an endemic problem with the round-top radiators, and probably why they changed to the square-top. I had the seam pop in both my 69 Dart and 65 Newport. Radiator shops confirmed it is a constant problem. You can fix it (I usually added solder), but will probably open again. On the plus side, aluminum radiators have become quite affordable.

If you want to keep the round-top look, one radiator shop soldered in an internal brace to keep the upper tank from spreading, which they said should fix it. It didn't recur, but after ~5 yrs I switched to an alum radiator.