Sorry for misunderstanding the question. With that in mind, I would also go with a cat back system and the Mopar Performance computer. The computer alone is worth 20+ horsepower and reportedly beter mileage (like two or three mpg). That would about eat up $500. I don't like headers on anything other than a race car. I've had them on trucks and street cars and they just aren't worth the hassles for the couple extra peak horsepower you get out of them. Whatever exhaust system you get, make sure it is stainless or has a lifetime, or at least acceptable warranty. There are cheaply made systems out there that will be rotted out in a couple years.
1983 CJ-7 Laredo