Guys I am helping a buddy put true dual stacks on his truck. The hitch in this project is he is buying 6 inch big rig stacks so there is no reducer from the 6 inch to 5" or 4". Plan right now is to cut that 3 inch under the floor boards, hopefully put in a 3 inch to 6 inch collector, run 6 inch pipes back to the bed, and turn up with either 90s or flex pipe, and then in to the stacks. Problem is I cant find any "collectors" in the size I need. Can any of you guys give me any pointers on where to find some thing like this? I can fab up some thing to work if need be.