Wait for the headers to come in, then spray some PB Blaster on those bolts the night before you do the work. They'll come loose then. I never beleived in that stuff until my brother turned me on to it. The very same bolts you're having difficulty with... I won't do exhaust work without it now.
If you're too anxious to get started, spray the stuff on now & wait about 15 minutes. I bet they come loose.
