[crazy longhorn]

with your stock manifolds, the restriction is 2".....I doubt that adding larger pipe at the rear will help perf, but will tend to make it louder. You can opt for a set of Vette centerdumps, to get to the 2 1/2" pipe size. A set of Dynomax Superturbos are a good deal for the bucks(good flowing, but not super loud). As far as the X pipe, they are better than the old H pipe......but will be d@mn hard to fit on your 4x4(I would stick with the H pipe). At the rear, you can cut the pipe size down a bit(if you like quiet), & you will be far enough from the heat that t wont hurt the flow. My 383 runs 1 5/8 tube Hookers, 2 1/2" pipe to the muffs, the H pipe is 2 1/4, & the tail pipes are 2 1/4(I tryed 3" tail pipes....loud as hell!) Like Mike said, the 383 pulls like stink right off the bottom, & runs to about 6000-6200......its running a 500 cfm Holley 2 brl, & a load of gear! Good luck,crazyL