Hi Pat,
Thanks for the input.
Jeff, over at Desert Aircraft, just emailed and said he found a header that has exactly the dimensions we need (says it the same as the 3W40 flange). I'm in contact with him now, asking a few questions about the header (straight, elbow, etc.). I'll post my results here as soon as Jeff and I get it nailed down.
Then you guys can give them a call and hopefully get the same thing

...Rob