Ditto the above posts, to also recommend the installation of an equalizing/crossover tube the first third of the new plumbing. In doing this, you will smooth out the pulses of exhaust pressure that are a result of V8 dual exhaust systems, and make for substantially less noise whenever you back off a throttle at highway speeds, increasing engine vacuum. A point to consider also would be to engineer it in such a way as to be able to "tune" the exhaust after it's installed. The simplest way would be to use 2-2.5 inch pipe, with at least 12" of die straight plumbing, again in the first third, that can be accessed once the truck is up on a lift. A little backpressure is a good thing, and in configuring it like this, you'll have plenty of room to be able to go in to that particular section of plumbing, and tack weld an oversized washer into the loop should it be needed. Another consideration is to not use stainless steel, as the initial cost does not warrant the overall long term cost of a standard piped arrangement; that, and it's damned near impossible to flame cut stainless cleanly, and thus makes any experimentation triple-difficult. Walker Hi-flow mufflers work well, (or did; I haven't been keeping up on hot rodding in a long time), and give a nice balance of rumble without an over-loud report that can grate on you after 2 hours, and seems to be like ringing a dinner bell for cops.