1997 Other Saturn Models Replacing muffler pipe

I want to replace the muffler and the muffler pipe on my saturn. The connection after the catalaytic converter is all rusted and the bolt doesnt have a head. Someone told me that its some kind of bolt with rivets or something. I wanted to cut the bolts off but i am afraid about hurting the converter, by tapping the bolts off after i cut them. Any advice on how to remove these bolts would be greatly appreciated.