Have you considered TTI 1 5/8"-1 3/4" step?
I have them on RHS/LA-X heads and they work great. The initial 1 5/8" section is not a restriction in most applications. In fact, some custom race combos start out at 1 1/2" and step up 2 more times. As you've probably read, the fit is excellent and they fit the 8 qt. Milodon pans. Most other headers don't.

Another thing to consider is that NHRA has come out with a new rule for multi-piece headers for 2014. Something about having to use an approved teather for the attached pieces. Not sure how far back in the classes that applies to off hand.