[Dominik]

If you like advise on header mounting, read on. If not ignore me :-)

Think flanges, 3/8" - done
individual header pipes - done
Studs with ARP serrated nuts - almost done ;-)
No fixed connection to collector/sidepipe to keep the vibrations away - done

No gasket! (worked for me)
This way the flanges sit from day one. May not work if your sidepipes are very restrictive

To fit the sidepipes once the header pipes take a set, and may warp a bit, I let 3 of 4 loose, slide them into the collector and tighten the primaries. This is when no gasket helps. I also had the slip-in length slighlty different so that one after another can be pushed in.