If you plan to deck/re-surface the block, then I suggest you consider drilling the holes into the deck (if you're sure you will be using heads with the extra cooling passages). You would need to find some head gaskets with the extra holes OR possibly drill holes into "regular" head gaskets.

70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"