Being as how this is in the block, I thought I would throw in caution. If you end up breaking a drill bits and ez outs in the broken stud... it can be incredibly difficult to remove. If you are not really good at doing this, I would bring it to a machine shop. Those guys have a lot of experience removing broken studs. I view myself as experienced but must admit engine machine shop guys know their stuff and it would not cost much.
Good luck to you.
84/87 NB, 3800SC, E-85, VS Cam, 2.8 Pulley, 4T65E-HD, HP Tuners, AEM Wideband, Regal GS Gauges, S-10 Brake Booster. 1/4 mile -11.85 at 114mph