Thank you 1LowGT. But looking at the heads I don’t see any plugs that are the same size as the ones in the block. There are 2 oil galley plugs in the block. One is just below the water pump, behind the timing cover. And the other is above the rear main seal, under the back cover. I think it is a 13 or 14 mm plug and look like small freeze plugs. Unfortunately so far I haven't been able find any information on these plugs. And the local Ford dealer parts guy doesn't really know much about what I need.