Turns out the dismantler’s directions were a little off. There are the four obvious studs on the side of the block and one bolt on the front behind the balancer just below the water pump pulley. There is very little room to work back there. The notch in the balancer only helps a little. In the end I had to remove the fan, fan pulley and shroud to get access, then heat and bend a sacrificial 12 point 17mm box end wrench grind it to clearance it and then apply a pair of vice grips to that in order to break the bolt free. There is not enough room for a wobble socket or even really a crows foot in there. I think the other bolts the dismantler was referring to were the ones that attach the alt to the bracket. Moral of the story, don’t over-tighten the alternator pivot bolt or you may crack your bracket and be stuck doing this job!