Ignition switch replacement (not the tumbler)

I just purchased a new switch for my ignition since lately the starting has been touch and go.
So i have removed all interfering parts but the problem im having is getting the part that attaches to the steering shaft off so that I can access the actual switch so that I can replace it. There are 2 headless bolts holding the clamp onto the shaft. Please help me out here.]

 

vice grips. this is very common as a theft deterrant. if you have a dremmel, you could cut slots to put a flat head. ive done it before by chizzeling grooves on the sides with a flat head, then further hitting the groves at an angle with a hammer and flathead in hopes to turn/loosen the bolt. it worked. but a pain in the ass. you'll need new bolts to replace those since they don't have any heads anymore to tighten down with.