If it where mine here are the options. #1 attempt to locnstitch it. #2 gas weld it with iron rod. #3 remachine a cap from steel.
Then with either a horizontal mill, boring mill, CNC horizontal machining center, or a very tall vertical mill the existing bore in the block could be reestablished. Easy stuff on the correct machine. Or someone good with a scraper could reestablish the bore in the cap. If that cap is fixed that hole will always need a hardened washer under the bolt head.
