Ass-uming you are going to be wheeling this rig and not mall-pozing like Keith the question again is WHY WHY WHY WHY WHY WHY WHY WHY WHY????
WHy spend all that time and money on an exhaust that you will beat the sh*t out of off road and will not give you any better performance than a single 3" exhaust (which is even a bit largish for a stock 351W).
If you really want a good exhaust (as opposed to a "cool" exhaust), get a good y-pipe/high flow cat combo (with bungs for the O2 sensors in the correct places), and then the cheapest muffler and tailpipe you can find, because if you go wheeling anough you WILL be replacing them in a couple years.
On my '90 I got a Bassini y/pipe/cat combo which very nicely tucks the exhaust up close to the body and places the cat right over the tranny crossmember for excellant protection, then I got a $30 Cherry Bomb "Turbo" muffler and 5 foot of 3" flex exhaust tubing coming out the back. The whole muffler and tailpipe are held on with clamps and bailing wire, so when they need to be replaced (the tailpipe is getting short from being pinched on rocks and trimmed off), I can have it all off in 5 minutes or so.
Of course if you just want to have "pipe fights" with Bubba and his 8" lifted '77 Blazer at stop lights then just ignore all this... :toothless