Type of Flowmaster Exhaust on a 84 pickup?

I have a 1984 Chevy pickup. I want a flowmaster that will give me good fuel economy and all of that good stuff, but I want a nice sound. There are so many different types, which one is right for this application?|||buy a magnaflow there better and stainless and have a lifetime warranty|||Flowmaster 40 series will sound great, but you arent going to notice a mpg gain with one muffler and stock exhaust pipe. Dual exhaust with non restricting pipe will barely give you a noticeable difference.|||40s are about the best sound you can get - if you buy them get duals put on that truck|||AS I HAVE SAID BEFORE, THE 40 %26amp; 50 SERIES IS WHAT I THINK IS THE BEST FOR OVERALL SATISFACTION !!