440 under car headers need advice.

For the life of me I don't understand why the headers topic gets so beat to death or people want to re-invent the wheel.

Buy a set of headers that are made for your application and fit properly. They are readily available. If you are building a big block dart and you are concerned about saving a couple hundred bucks on something as critical as headers (that trust me, you want to last and NEVER change again) this might not be the build for you!