Tons of theories on exhaust. Most of it boils down to personal taste.
First, unless you put some money and work into your engine, the headers will not
live up to their full potential.
Something you might consider is to keep the majority of your current system and
have the exhaust split back out to duals just before the rear axle. Sure it will not
be a true dual system; but you will still have the dual outlets, which is a major factor
in the "dual exhaust" sound. Also, as the exhaust gas heads towards the back and
cools off, its density significantly increases. Which means it doesn't require nearly
as much volume to move the gas at low pressure, as it does at the front of the
system. The cost of just a Y and another tail pipe would be considerably less, and
still get the look and sound you are after.
I am big fan of glass packs! They are cheap, have a great sound, flow better than
anything, hold up well and are easy to fit. The trick is to get the right length.
Too short and they pop and cackle. 32"-36" is great, no pops or cackles, deep,
mellow sound, you will not go deaf on the highway. The glass pack design will also
help channel most of the sound out the tail pipe, with very little coming up through
the floors and into the cab. These trucks have very little sound insulation. This can
make a huge difference to driving comfort. Flow Master might sound great as they
drive by, but actually flow awful, are very pricey and will drive you insane on the
highway. Their thin, uninsulated cases allow a lot of sound to come up through the
floor. I have dual 40" glass packs on my 5.2 Magnum, I love them! Healthy, deep,
but civilized and tolerable sound. They are still new, and will get even better with
age. You don't want straight pipes. Besides being illegal, it will sound awful. You
don't want to be in the same crowd as those Chevy neanderthals that run around
like that, thinking it makes their crumby 350 sound good.
They are pricier, but Cherry Bomb also makes a Vortex muffler that is awesome.
They are pretty big and heavy, compared to the typical turbo muffler, but
have a very non restrictive path, and the heavy case pushes all the sound out
the back. I have a pair on my convertible, with a 440. You can hear me on the
highway a mile back when I get on it, but still maintain a conversation without
yelling at 70 mph, with the top down.
Muffler location tends to be at the front because the longer the tailpipe, the
smoother, more uniform the sound and generally effective the muffler will be.
More importantly though, as the gas cools condensation forms from the water
vapor. The closer to the front, the more of that water remains in vapor. The
closer to the rear, the more condensation and the more likely that water will
condensate in the muffler and rust it out. Ever notice water dripping from the
tail pipe?
I am not an expert on fluid dynamics, but I would imagine that some muffler
designs would do better with the fast moving, hot gas up front, while others
would do better with the colder, slow moving gas at the rear. Efficient exhaust
is all about balancing the scavenging effect of a high velocity flow of gas, with
the proper amount of back pressure. This is especially true on a truck. extremely
low back pressure is great for high rpm horsepower, but can impact low rpm
torque. Torque is typically much more valuable for a truck than horsepower.
