I will be getting my 360 back soon from being built by Joey Arrington. For those of you that do not know who he is, do a google search on him. You will find that he is one of the, if not the best authority on MOPAR small blocks in the world.
The engine he is building for me is going to produce somewhere near 590 horsepower. And guess what... it will be set up to run the TTI 1 5/8 - 1 3/4 stepped tube headers at his recommendation. The same headers that you guys are questioning for use with higher horse power engines.