VectorSolid:

I assume you have contacted Clifford? Also if you haven't seen it yet, I made a set of headers for my motor, Willys F-head 6 cylinder... Search DIY headers. I made a cardboard pattern for the flanges and started there. Drill press and hole saw through 3/8th inch steel...No fancy tools or equipment necessary. Used u bends available from several sources.
So, I second Nexxussians advice.

Sincerely:
Paul...aka xerxes