I ran them for a couple of years on my 496" low deck in the Barracuda. They were ok, but I picked up a lot when I built my own headers. Of course that engine was set up for 7600 rpm shift points and was never a street car. If you are putting it on the street sell the pro parts headers and put in TTI's or better yet, for ease of install the try y types. I have a friend running these and loves them.

Try Y headers

-Dave