Last time this happened to me, (depending on how big the bolt is), i just spot welded a smaller nut onto it and then turned the nut and the bolt turns out. Dont know if you have a welder or if the bolts even big enough.
I really don't know what to do with this. It looks like the bolt has become part of the block. like there was not even a bolt there to begin with?
isn't gonna be a pain to drill and tap it?