[nxtruck]

To the O.P.,
you may try calling Tom Dawson Racing Headers. About 15 years ago, I had them make a set of 1 7/8 x 3 1/2 custom headers for my '66 with a sbc, and the headers fit like a glove. Tom used to be an engineer for Hooker and he would take a set of headers for a specific application, set them up in a jig, and duplicate those headers in whatever size pipe you want. I have nothing but good to say about them.
Their shop is located in Nuevo, Ca. and their number is 951-928-0969.
Good luck with your build!