A little background on how we got here.
Car is new to me. 62k mi, 1999 model year.
Looks like someone forgot to install a gasket on the thermostat. I've replaced that and the water pump and didn't realize there was a head gasket leak until I got everything up and running with new coolant. I suspect the car overheated and caused this mess.
I've attached a picture from the borescope results referenced from the last message. The is from the first cylinder. Bubbling is at the seam between valves and cylinder wall.