So why is the OP replacing the heads? I might have forgotten by page 3, but it seems like an important question. I hope you checked the block out first for compression. And I hope it was not for anything like a blown head gasket without a tear down first to confirm the new gasket has a good surface to seal to.
I still wonder if a new set of iron heads is a better deal. Which is more important - cost and better heat/ blown gasket resistance, or 40 less lbs and running a little more compression? In short, if AFR, Dart, or TW offered iron at a good discount, I would be tempted to use them. Then spend the extra on Weight Watchers and blow all the weight savings with a small but custom woofer box.