That little casting on the pan rail didn't have anything to hook to on my 544 so it got plasma cut off.
What I'm running is a FI manifold and 140 headpipe. The reason for interference is that I had the manifold angle milled to sit closer to the block back when I had the Judson supercharger(Cameron and Phil will remember that one). I also had the FI manifold coated after spending an evening or two smoothing it.

It might take a pretty nice header to make me switch, and I'll likely make my own as detailed on my web page: http://www.geocities.com/iadr1/techphotosmystuff.html . I'm aiming for a very small tube stepped to a slightly larger tube, and a major change at the gasket surface and port. I have most of the parts, including a trick 4-2-1 collector and .500" thick flanges, but it's just not a priority right now.

The primary piping on the new IPd header is 1.5" OD, correct?
I've seen the old T-bird header on Ebay, and is was a really nice piece. More complicated bending than others though...nothing wrong with that- adds ~$10 to the price and makes it look nicer.
I for one would love a pic of the new IPD-T-bird design.