Check the head with a straight edge, you should be able see any warp, then check the headers. IF your headers are like the two that I have, the pipe has been welded to the flange on the head side. You can flatten out the welds some depending on how good you think the weld penetration is. Use two gaskets and hi temp RTV on all three surface. Torque down, run to a good temp, re-torque. That should help. The next set of headers I get will be Fenton.
Larry