Hello everybody. This winter I am going to do some exhaust work. I am going to install headers, new cats, y pipe, and new pipes back. First question, does the truck have four cats, or two? Next question, what size should I make everything, 2.5" or 3"? I already have a gibson cat-back.

My truck is a '97 f150, supercab, 4X4 orp, 4.6, 5spd.
Thank you for any help.