I wish the head pipes were held on with nuts. Pontiac used bolts. I could just heat the nuts with a torch, but the bolts are buried in the manifold and that is lot harder and more risky to try to heat. I wonder if anyone has had experience with this. I have an air impact wrench and could start at low torque and work my way up. I don't want to have to drill out a twisted off bolt.Like any older car the nuts may have rusted onto the studs. You can try penetrating oil sprayed on and also a soaked rag left on for 24 hours. In worse case scenarios heat has to be used. I recommend upgrading to a 2 1/2" exhaust system with mufflers suited to your tolerance to potential drone. Below is an example.
Price is WITHOUT Mufflers! Choose a pair of mufflers to the right. Part Numbers SGA12R - System with Race Pro Mufflers SGA12S - System with Street Pro Mufflers SGA12V - System with Violatorpypesexhaust.com