Exhaust questions

[old Rusty C10]

1982 C10 5.7 motor Edelbrock intake and carb
Im looking to have power and the best possible gas mileage
my exhaust is kinda shot. The manifolds are there as is the Y pipe and it feeds down into something that kinda looks like a cherry bomb muffler then that goes into the intermediate pipe which is rusted and the muffler and out the dual tail pipes..
for now im going to go to the local chain and get a cheap walker muffler intermediate pipe and the dual tails and that should cost me under a hundred dollars if i install it myself .
In the spring im going to want to put a decent exhaust on there.
Heres the question I wanna put back the A/C compressor and the rest of the air conditioner back. I was thinking of Headers and some kind of mufflers then straight out the back under the bumper. I dont want to have the truck too loud either and i dont wanna spend more on the exhaust than the National Deficit
any ideas? Also ( now im getting old and senile) but its been a while since i built a truck but are there certain brands of headers to stay away from due to the fact they warp when they get hot?