I made my own custom brass stepped washers to apply equal pressure to the two different flange thickness between the header and the intake manifold. I made longer studs to accommodate the stepped washer and the double man-a-fre header gasket that I soaked in warm water for about 1/2 hour to soften it up. I had previously planed both the header and intake on a big piece of glass with sandpaper to get them flat. I also use stainless nuts with hi temp anti seize compound torqued in 1/3. After I heat it up good by driving for a half hour I retorque them again. A few weeks later again a retorque. Been there a long time and have never leaked.