[olddog]

You might get better help if you described what is so hard about getting the bolts out.

If you can get the bolts broke loose and the problem is that the bolt heads get too close to the pipe as they back out, then the solution is to loosen all bolts at the same time, and keep pulling the header flange up against the heads. Loosen each bolt a turn or so at a time to keep them up close to the flange.

Hope that helped.