u will need a cordless drill for the job probably, but if u have a angle corded that would work i know when i drilled out mine in my brat that i used my dads DeWalt 18v drill with a worn out nicd battery and it worked pritty good(my 1/2 corded black&decker hammer drill wouldn't fit:mad:sadly i used it so much i broke it a couple months later) but this time i used my craftsman c3 lithium 19.2v and it worked fantastic, i prefer corded so i know if u dont have a cordless but my craftsman gets alot done in a little time and its easier to handle

I have an 83 Brat with the same ignition as you.  My key wouldn't turn so I dismantled the key end from the ignition switch end.  It should be simple to pull apart.  The ignition switch is the thing that has a few wires soldered to the back of it.  The front of it has a rotating blue plastic piece with a T in it.  In TurboSubaruBrat's last picture the very center horizontal nub thing is what fits inside the T to turn it to start the car.  Then, like someone said above, you can use a screwdriver, sharpened popsicle stick, whatever to rotate the blue piece clockwise. 
I can't dismantle the right side(actual key side) of the switch but I'm going to try drilling out that pin tonight.  I'll let everyone know how that goes.