I just used set screws in my alu. heads. You can get them in most lengths and you have the benefit of being able to use an allen wrench to install them. I think i used 2 inch in mine, that way i can use all the head threads plus gasket thickness plus 1/2 header flanges plus another 1/2 or so for a lock washer and nut.Just be sure to use some anti-sieze on them. Randy

1957 Dodge truck, Snakeskin Green with a little stroker motor. 1964 Plymouth Savoy wagon ( my new project)