Sorry about originally saying the leak is at the top of the radiator, it is at the bottom.
Mechanic showed me the wet area below the radiator near the bottom hose. I told him that I pull the hose off to drain the radiator during the yearly drain and install of new Prestone and if I don't tighten the clamp tight enough it leaks something like that.
I, and the mechanic, will know more about the leak when the radiator is removed to be repaired and whatever else they do to rejuvenate a radiator. As I remember this is the second time my truck's radiator has been repaired.
Noticed a few years ago that the round disk-like supports/bumpers below the radiator looked like they were getting old and possibly failing. Assumed they were not important because the radiator is held from above but maybe not.