to see if im in the ball park with good manifolds is to take a known good straight edge and place it across each manifold and check for full contact across all three flanges. then bolt the halves together at the heat box but loose enough to wiggle the manifolds and put the straight edge across all six flanges and see if contact is made. my manual says .10 max allowable misalinement of flat surface. ive been able to seal mine with positive results even without alignment rings but its much easier if you have them. ive also had to get them milled flat as a unit in order to get them to mate to the head.
