I am going to instal the 68-70 340 high perf exhaust manifolds instead of the Mopar Performance headers that are currently on the car. The headers have been flattened out on the drivers side bottom 2 pipes as you all know can happen on the A body. But I am concerned about the HP loss when I do this. Putting any kind of header except for TTI's on the Dart is a real pain in the butt and am not looking forward to doing it all over again. I have the manifolds and would like to know how much power will be lost or is it going to be negligable and not really noticeable. Anyone out there do this "backwards" installation?