TTI system questions

Is there two different H-pipes for A bodies? A 108" & 111" wheelbase versions? The H-pipe for my Duster seems like it's too long. Do I need to cut 3" off?
Also, everyone will tell you to start with the tailpipes when installing a TTi system. That will work great if you have headers, but if you've got manifolds, you're going to need to start at the front and work back. So have the Magazine gurus never installed the system for manifolds?