Doug, I believe the options you have are: deck the block to get rid of the o-ring groove, put copper wire in and pound it flat , see if the ring on the std. head gasket you want to use will seal up with just the groove, or run copper gaskets.
I would probably just run copper gaskets if it were mine, but I haven't run them before. You might PM Zipper on here. He runs blown combos and probably has as much experience as anyone on here with o-rings.
Curtis