All depends on what you want in the end. Are you going to run your headers into a single or run dual pipes? If dual, will you run a crossover pipe between them? For a classic sound, my preference on old trucks, I would run 1 3/4 dual pipe, short glasspacks and no crossover. For a more modern sound you could go with a pair of flowmasters, still keep the pipe small and use a crossover pipe, or if you want a single go with 2 1/2 pipe and a modern muffler of your choice ( i like Borla myself)
Devin
