Swapped in new radiator and water pump. No leaks so far......*
And, the loud noise was the water pump bearing, and it's gone now.
Now I can RMA that Champion all-aluminum unit.
Kinda surprised that one of the two new "8.8" bolts for the thermostat housing that came in the Gates water pump box stretched when being torqued to 11 lb./ft. I had to reuse the bolts that were there, but they did fine.
I wanted to also do an oil change and swap the pads/rotors, but after burping the coolant system the oil was too hot to play around with, so I went inside to cool down. This was three hours ago and I already cracked a barley pop, so I'll probably not get to that stuff today.