Thanks for pics! Great idea with the header flange on the down pipes. Looks like they were added on without being shortened prior to welding? I would think you shortened the pipes leading to the muffler?
I just added the flanges to the ends of the down pipes.
If you look at on pic, I actually had to add about a 6" section to the drivers side pipe after the flange, because the down pipes are shorter than long-tube headers.