Unstoppable Coolant Leak

Do you know if block was ever milled when it was bored? If it was milled and now with heads being milled it's more than a .010 drop.

I bought the block off a guy with the machine work already done. He said the deck hadn't been touched, but all I have on that is his word. That could also caused detonation problems as well couldn't it? I was thinking maybe having iron heads was playing a huge role in it but more compression than what I thought could as well...