I just put this system in my truck bolted up to a set of the Summit ceramic coated headers.
http://www.summitracing.com/parts/WLK-89007/
The intermediate pipes fit well and flowed well with the frame. Only issue with them was the slip fit on the header flange had to be stretched out a fraction more than it was. Muffler fitting slipped right into the Thrush Super Turbos I bought. The tailpipes on the other hand took some tinkering to get working right. The shop I had welding them up had to make 2 extension pieces to get the hump centered over the axle. All in all the Dynomax isnt a bad setup, but those tailpipes would be frustrating if youre on a creeper working underneath the truck.
I dont have any feedback on the hooker system, but figured I would throw out the Dynomax info in case you looked at it too.