Did you bore it .030 or was it already bored and you are re-ringing it? If it was already bored before, I would not use anything but cast iron rings. Did you measure the gap at various points. You could get different gaps if you have taper. But here again it depends on if you have a fresh bore. Since aluminum expands more than cast iron, I think you should have a little more clearance in the groves to keep the rings from sticking when the engine is hot.