The FlowMaster muffler was just another muffler brand until the late model guys started installing them on their 5.0s. I can remember hearing them when this first started and all that I can say is the rest is history.
The most popular of their mufflers then was the two chamber Series 40. There is just something about a Ford V8 and the FlowMaster that delivers an aggressive tone that's just right. Yes, there's interior resonance and the neighbors will know who's car it is, but FlowMaster now makes several different designs so that you can tailor the sound to your liking.
I like to hear my engine and I have bought the new two chamber Super 44s to replace my old two chamber Series 40s. They are supposed to deliver an aggressive tone above and beyond the the originals. I haven't installed them yet, so I personally haven't heard them.
As we all know, it all boils down to a personal preference, but the 5.0s got FlowMaster on the map. Check out their web site.
www.flowmastermufflers.com
Long tube headers will add to the muscle sound. Use an "H" pipe type crossover to balance the exhaust pulses. An "X" pipe will smooth out the tone which is similar to the sound of an exotic imported engine, which is probably not the sound that you're looking for.
You also can go the route of installing a repro Shelby exhaust system which will give you the original sound of the 60s. You will need to get a set of repro cast iron 289 HIPO exhaust manifolds or go to Shelby's Tri-Y type headers also available in repro form.
Another reason that I like the FlowMaster is the fact that they don't use any packing inside their mufflers. Regardless of claims I just don't think packing in mufflers is going to last over time.
trying to get the best sound out of my 1965 convertible 
and i am just wondering what you guys think is the best way to make it sound like true muscle. im talking anything you guys think would work or anything that you guys have done.
