Would it be hard to install a 5" exhaust system for a 2004.5 to 2007.5 model onto a 2008 6.7L?

 

depends on what kind of exhaust it is.

 

I was thinking about RBP 5" with the black finish. If not that one do you know of one, maybe one with duals.

 

you need a system to trick the emissions controls or your truck will go into limp mode and you will be in trouble. Look up DPF delete and you will see lots of info. Also look up H&S exhaust and BADP. they are the 2 most popular systems for these trucks.

Chris