I am in the middle of rebuilding a motor. The motor is original, never rebuilt, just shy of 60 years old.
My machinist is a young guy, terrific really. Tolerates all my inline nonsense. I was ordering some parts. Now mind you, the core plugs were not leaking or damages, I just replace them as a matter of course and I have a couple of the Pioneer kits in steel at home.
He was recommending a brass freeze plug set because it was more rust resistant. I am 64 so I said bless your heart but I wont be around when the steel set I am installing goes bad, lol.