Well.. The USPS system in Bristol Tn. must emoloy the FEDEX rejects. They have broken three items for me in the last few months. All marked FRAGILE, all from different parts of the country! One even showed up delivering drunk! Haven't seen him in a while.
Believe me, it's the easy way to go. I bought a set of crappy headers at a swap meet for $35.00 and used the flanges from them. The port shape is really hard to match and look right. It's worth the extra effort not to have a sbc like everyone else.
Good luck and MERRY CHRISTMAS
I have done this twice. Hooker and Hedman both make flanges with a stub already welded to each port. Due to the port shape, this will save you bunches of time and look good too. Get some flanges--the rest is cake.