Truck in question is an 86 F250HD Super cab, non-cat truck, emissions exempt. Currently 351/C6, may become a 351/Zf5 or even a 393/Zf5... 4x4, A/C, PW, PL, etc 33" tires, 4.10 gears.

It's going to be a work truck/toy so it's got to be able to work, which includes hauling 2-3k in the bed from time to time and towing 6-7k trailers from time to time.

As for noise, I've got a Harley and a Mustang with Borla stingers so I've got loud covered. I want a little bit of a throaty rumble but it should be fairly quiet.

The truck has true duals, 2-1/2" IIRC and Supertrapp mufflers. I haven't heard it but I'm sure it's a heck of a lot louder than I want. Actually I suspect it sounds like crap, but that's just a guess...

So here's what I'm thinking. Shorty headers, 2-1/2" mandrel bent Y pipe into a flowmaster Y. 3" out, 3" Flowmaster 70 series muffler with a single side exit. I'm probably going to buy their kit for the 94-97 F250, then build the Y pipe to meet up by stitching together various pre-bent pieces.

Which is louder, 50 or 70 series big block? Any benefit with one over the other?

Sound like a winner? Is there any reason to stay with a true dual setup and just throw in some mufflers and extent the tailpipes other than cost? They're straight out the back and while I used to love the idea, my Dodge has that type exhaust and it does nothing for me anymore. A well designed exhaust that's tucked up and out of the way is much more impressive than some loud trumpets sticking out the rear...

Don't get me wrong, I like loud, just I'm envisioning this truck being a little more mellow in the exhaust department. As it stands I have nothing I can sneak around in late at night....

 

If your going to have loads in the bed and towing fairly regular like....you'll be happier with long tube headers (LT), rather than shorties. they, LT, provide better scavenging affect in the low to mid range RPMs, where your gonna want better response and be for the majority of use. the Shorties are improvement in the upper deck of RPMs only.

as for mufflers, that is your choice...youtube is your friend here. Generally speaking the the higher # FM you get the quieter they are.
Seems like you be better off with the tips out the side, not straight back! To avoid exhaust sound bouncing off the trailer (reverb)...the size is about right...wouldn't go 3" in dual configuration...single only. 18" maggie would be nice too.

 

Back in my Fox body days I was told that LT headers would kill low end vs shorties. I was told that the H pipe basically acted as a giant collector extension. Longer collector, more torque boost down low.

I was thinking of a set that basically replaced the stock manifolds, not the intermediate length ones I've seen.

3" single sounds good size wise?

How about the Magnaflow Y pipe? It's much smaller than the FM but supposedly flows better. The one thing I don't like about the FM setup is it's aluminized steel. The Magnaflow one is SS. This way I could make the whole system SS if I wanted to.

 

Long tube headers vs. short tube headers.

your mustang isn't going to pull trailers...realistically speaking.
the mustang is for horsing around and racing...it likes the upper RPMs for the power.

your truck is a different animal doing far different things & needing power in a different power band. but pretty sure you know this.

ya 3" single would do and may seem better for the trailer end

check this out...pretty well gives the pro and cons THE Exhaust Guide - F150online Forums