There are sites on the net where you can find out how to pull out the steering lock with a slide hammer. You can then crack open the plastic behind the steering wheel and engage the starter switch with a screwdriver.

Junk yard guys do this all the time. I have not needed to scrap out a 90's GM anything for a long time, so the finer details are no longer with my memory.

But just do a bit of Google searching on this topic. This is an everyday thing to those in the business.