yeah, i always just used the center punch/chisel to get them out at work, i dont even bother with a G-Clamp on it, once the chisel grips in, well they can turn siezed bolts that will round with a single hex socket, so it shouldnt be too much trouble to undo a sheer bolt, and we do the same, just a normal bolt in the new one, same with BA ECU's, they have sheer bolts holding them in, we just use a hacksaw blade to cut a slot in them, and then use a flat head, and once again, just a normal bolt back in. And yeah, those ign barrel slides are a paint in the ass lol, i cant imagine having to do it by trial and error but