My last set up on my 351w was stock manifolds, stock piping up to where it was supposed to be a y. Made a better flowing y pipe into 3" pipe then into a 3" single in single out flowmaster 50 series and a 45 out behind the passenger rear tire. Sounded like a mustang with a 302 if you cut off the exhaust after the cat on it. No crackle or pop. Mellow under 3000 rpms and a nice roar after that.
My current set up is a set of long tube 3" collector dynomax headers into a 3" single in single out summit street and strip muffler then it goes to a 45 degree angle out before the rear tires. Sounds a lot meaner and lower, but still decent at low rpms. The headers with the full 3" pipe and lack of tailpipes freed up a ton of power. You can tell a difference in the seat as well as in the pocket. gained 1 mpg average swapping to the current set up.
I cut mine off just before the cat ran a piece of 3" pipe into a 3" in flowmaster super 44 and a 3" turndown directly after muffler which is just infront of the rear axle.
Search "thebudmiester" in YouTube i have some exhaust clips there
I've got a 94 with a 5.8 and factory manifolds, Y pipe and cat. 3" from the cat to a magnaflow and then 3" out to the rear of the truck. Sounds great and I make good power. It's a simple and inexpensive exhaust. Not sure if the truck gained any extra mileage with my setup as my dad did it before he gave me the truck.