First thing is to have the block magged to see how far and bad the crack is.We have seen and have repaired blocks similar.Some can be welded and tubed to seal the oil passage.It's tricky since the tube needs to be open to the cam and lifter galley.We just had a block come in that has a repair but shows a crack on the oppsite side of the hole.
The hard part about any cast iron repair is where the weld and iron intergrate it becomes hard and is difficult to machine.Repairing is easy,machining becomes difficult but with the new process,s available a good skilled welder can repair most anything.
If this block is a factory numbered block and is destine for a restoration project that must have(the correct,original part) then repair it.