1st Time stack install - help needed

Hi I am looking for some guidance on installing a used set of 5" stacks I bought. They are going on a 2004 F-250 crew cab short bed 4x4. I have the stacks, Y-pipe, and the piece that connects to the Y-pipe under the bed. The piece under the bed is 4"x2`long and has a reducer on the end from 4" to 3.5". My questions are anybody know what I need to run from the down pipe to this piece I have? Is there something preformed I can buy to do this? Do I need a new pipe coming off the turbo or can I tie into the pipe just before the Cat? The pipe coming off the turbo is 3" and has some kind of heat wrap around it. The Y-pipe is 5" stepped down to 4" where it goes through the bed, what hole size does everyone recommend through the bed? I am going to use two clamps to fasten the Y-pipe to bed, do I need something on each pipe to fasten them to the bed? The brand of stacks is RBP 5" bullhaulers. Thank you everyone for your help this is my first stack install.:read: