I have the gibson 301S headers (just like JBA's) on my other dakota (same motor as your ram) going to a 2.5" downpipe/y-pipe setup into a 3" cat with dual 3" tailpipes. These aren't race trucks in our cases but still, these motors have to breathe well. Going big won't hurt it, although if you're mostly stock a complete 3" system might be a bit overkill...