5.9 performace mods

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...

I'm looking to convert my stock 5.2 to a 5.9 and seeing what ugrades I can do to the 5.9 that's seems to work best. I read that they are interchangeable as long as the years are close together. I have a cold air intake and a throttle body spacer on my current 5.2. Any ideas as far as cam kits or...