Those can be a real pain. Check out this TSB:
http://www.q45.org/gallery2/d/...05f9f
The ignition switch is held on by a "U" shaped bracket. The bolts are actually shear head... so when they were installed, the head broke off. This is an anti-theft measure.
So you need to drill the heads off... look on the bottom side of the steering column. You can just replace the old bolts with regular bolts, allen cap-head bolts, or order new shear head bolts if they're available.
Good luck!
Heath