Hi, I am new to this forum thing, but I can tell you.....
headers are the first choice to use when enhancing an exhaust system. They will give you a lower exhaust growl mainly due to the increased distance of the exhaust runners on the headers, also there is an increased efficiency in scavenging which in turn leads to increased power levels. If you have a non-Cal. truck you already have duals and I would not recommend going larger than 3" unless your going w/ a single pipe otherwise you risk losing low end torque. Glass packs on a v-10 is, in my book, a no-no. It will sound like an airplane. Also, one last thing, if you use headers I would recommend an H or X pipe crossover. They would go app. 18" after the collector or where the gasses are hottest in the exhaust pipe.( on ss pipe it will be discolored in that spot and that is where to put the xover).