As "Stroker" McGurk replied when asked how many "thous" he had removed from his Flathead V8 heads: "Thous be F----d! I took off an 1/8th of an inch!"
You guys watching this exchange will now be seeing all the ramifications of hacking & slashing at Opel blocks and/or cylinder heads - OK for cunning old sods like Bob, Jeff and my humble self BUT if you can get away with out touching those surfaces then you will not have to sort out all these cunning methods to put things back where they should be in the first place!
Sometimes it has to be done when engines are modified away from 'factory stock' but if you can avoid going into this mine field then do!