My grandpa who's an old racer that knows ALOT about mopars told me a while ago that when you bore out an engine, bore only what is needed to make the bores nice, if it only takes 30 over, bore it 30 over.
x2. A thicker cylinder wall will make more power than a larger, but thinner one will. Iron does flex and the thinner it gets. the more it flexes, and the ring seal is negatively affected.