This is good info!!
The intent would be to " chase & clean " all bosses of the block.
Any problem threads ( boogered, stripped, chipped etc ) I would leave alone, save for the machine shop if I were to come upon such monsters.
I, too, was taught that when working with threads & hand tools, go slow, back off & clean the debris, use something for lube.
Thanks folks, I Greatly appreciate the feedback!!