Thought about slotting the bolt holes vertical to shift the opening up. My other thought was if a machine shop could surface the raised area flush down to the 5/16" thick flange area and basically turn it into an exhaust manifold type seal. But how/where are the tubes welded to the flanges? Are the tubes pulled through hammered out then weld bead built off that is now my gasket area? Or is the pipe welded inside the opening of the flange? Only then could they be surfaced.