I don't know what a cross section of the engine mount looks like, but why not drill and tap new holes? If it's hollow it would be a simple matter to fill the cavity with JB-Weld and drill and tap that
Thanks for the replies. I proceeded to extract the other mounting stud in the block. I will now use a #2 screw extractor for removing 6mm screws. (not a #1) The embedded piece of #1 screw extractor in the other stud caused the drill to wander. I had an old grubbee carcass in my graveyard and found that the engine bloc was solid where I was able to drill and tap a new stud hole. Then, using spacers (nuts) and a bracket I re-constructed the original stud spacing. Thanks again