Broken keeper pin in differential

[cheford]

I've got a rear differential from a 1990 Silverado that I'm trying to disassemble and the bolt that holds the pin for the spider gears is broken and I can't figure how I'm going to get it out. I've thought of drilling it out but there is seems to be no room for the chuck of the drill because it is so close to the casing. I'm sure someone has run into this problem and sure would like to hear from you.