Well, your block is aluminum. So my preferred method is to use a mig welder. You can stick a nut over the top of the hole and build up weld inside of it. It will only stick to the bolt and won’t stick to the aluminum block. The heat will also help break the bolt free.
If you don’t have access to a welder or someone who can do this, you can drill the bolt and try to use an extractor. I usually have mixed results with this method. This method only works if you have room to get a drill where you need to.
The last option is drilling the bolt out and either use a heli coil or drill and tap it to the next size. This isn’t soo bad if you’re careful, but I’ve seen far to many instances when someone has drilled too deep, wallowed out the hole, etc. So be careful if you do it.