5.9 exhaust

HI everyone, I have a 1998 ram 1500 sport with the 5.9 v8 and I am looking to put on a whole new exhaust system. I am looking at headers a new y pipe as well as hi flow cats and a new muffler. what performance gains should I expect as well as mpg, what am I looking at as far as price is...

Does anyone have any experience with/ opinion of these? The price is great. The specs match JBA's Cat4ward Shorties. http://www.ebay.com/itm/271054068617?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 Currently for sale on ebay.

I have a 98 ram 1500 with a 360 that needs a new exhaust. I plan on making it into a true dual, I figured out how I'm going to run it and what mufflers I'm going to use but I'm unable to pick the right cats for my truck. I'm looking at flowmaster and magnaflow cats and they offer quite a...