I'm not losing any sleep over Magnum heads cracking. Every Magnum engine I have ever torn down had cracked heads, every one. I have never had to tear down a Magnum engine because the heads were cracked.
lol Thats some good luck, i had two cause misfire codes and had to pull n replace a single head and then another both. Exh seats each time and nothing/no issue leading up to that.
I know what you mean though, just press a seat when the crack isnt too bad.
J heads crack too, for me i had a set that were cracked on the outside exh flange...i couldnt believe it