My old , cobbled together exhaust finally had a come apart on me. Out with the old, in with the new.
I ordered Pace Setter ceramic coated long tube headers, off-road y pipe, 4 feet of 3 inch pipe, Walker quiet flow SS muffler, a weld on turn down, and some other little things. I still had a good set of manifold gaskets from building the 408. The gaskets that Pace Setter gives you look like junk. I would recommend buying a good set when you order the headers.

Header install:
Passenger side; hmmm, might need a piece of rope to keep this thing from falling through and hitting the floor.
Drivers side;
EFF THIS MOTHER EFFIN PIECE OF EFFING SH... Who decided to put long tubes on a 4x4 anyway. Lol.

The passenger side slipped in with no troubles. I didn't even need to pull the plug wires. Bolted on perfect and was ready to go. The drivers side on the other hand was a nightmare. (It looked like they let the jig sag when they started laying the pipe.)

First off the master cylinder, starter, and front drive line needed to come off, along with the plug wires, plugs, and anything else in the general area tied up.
There was a 4 inch hole under the starter boss on the bell housing to slip the collector through after getting all this stuff out of the way.
AWESOME, it's in there. Let's start a couple bolts and check for clearance. Nope, try again... It's hitting the starter boss on the bell housing and leaving a 1/2" gap between the flange and the head. Look at the drive line, even worse. The collector is about 2" into the drive line.
Take it out and get after it with the BFH. After beating on these pretty things, I can now get most of the bolts in. Once I have most of the bolts in and tight, I took a bottle jack and put it between the collector and trans. This moved the collector and tubes over about 1 1/2".
Now there is some room around the bell housing, but I still need to hammer more for the starter to clear. Pull them, thump on them again (felt great this time because I was mad lol), reinsert. Now there is room for the starter. There still isn't room for the drive line at this point. If I smash that tube any more, there won't be any air flowing through. I'm lacking about 1/2" still.
Now I have to get creative. Using the same pushing method as before, I put a piece of 1x4 between the tubes and the frame, about halfway up. I didn't want to blow the trans mount out from pushing, so I added another Jack on the other side.
Once I pushed the collector to the frame against the 1x4 above, it finally moved it about where it needed to be. With the hammer work and the jacks, I now have a little over 1/2" of clearance all around.
Loosen it up enough to get the gasket in and we're ready for the next project... Y pipe.

Y-pipe:
This y-pipe is awesome and simple. With that said, I was still fuming over the header and couldn't figure out how it was supposed to fit together. Thankfully my wife is a lot smarter than me and showed me the error of my ways. Lol.
It showed up in 3 clamp-together pieces. The passenger side has a slight offset for fine tuning the position. The drivers side pipe goes over the cross member, between the t-case and frame. The last piece looks a lot like the stock y-pipe as far as shape goes.
Even with all the fuss I had with the header, this went together fairly smooth. Once I knew how the passenger side tube was going to sit, I marked and welded 2 sensor bungs in (wideband, and down stream). The passenger header has a bung in it already.

If you're keeping stock exhaust after the y-pipe, this is the point where you would mark and cut your intermediate pipe, weld it up and call it good.

From the y-pipe back, I cut a 2' piece of pipe to move the muffler behind the skid plate mount, then cut another piece about 10" long to go between the muffler and the turn down. Once positions​ and angles were set, I welded all of that up.
I used exhaust mate universal hangers to keep everything in the air. These hangers claim to be good for 1-3/4" to 2-3/4" pipe. They fit really well on my 3" stuff (tight, but still easy to slide where needed). I don't think they would work with anything smaller that 2".

I haven't driven the truck enough to really see how they'll do, but the throttle response is really snappy, and the truck with it's 408 really rocks when you goose the throttle. I'll try to add driving notes as time goes on. It now has a nice mellow rumble up to about 4,000 rpms with a sharp rasp above that. We'll see what it sounds like under load.

Thanks for reading my novelette. Hopefully this might help someone installing headers on these trucks in the future, and gives you folks some laughs.

 

I think no headers are direct fit, They all need "massaging"! I had a set for my power wagon(mopar performance, only ones made for it at the time) that came with a hole(weld blow threw) and one of the collectors pointing up. What where they thinking when they where welding them? Quality control is non existent!

 

When I put my JBA shortys on my 98 durango 5.9 they fit pretty easy. Now getting the back bolt in and started was a different story.

 

I would have to agree. Every long tube I've ever put on needed some help, just never this much. QC I think is "yup, it's all shiney. It's good". Lol

Shortie's would have been easier, but Flyin'Ryan suggested the longs.

After about 50 miles of driving,(30 miles highway, 20 miles of 2 track playing), I'm very happy. The throttle response is very aggressive. I have to be very careful taking off now or I spin the tires. Lol.
As for sound, it has a nice deep rumble from idle all the way through the rpms under load. This thing has never been this quiet in the cab. No drone at all, and only audible when stomping the throttle. I never realized how noisy BFG AT's were.
The next thing to watch is change in mileage. Im curious if these will help or hurt after I quit playing with the skinny pedal.

 

Yeah, expect mileage to drop initially. Then see what happens.

 

Two fill ups into it, and I'm seeing a bit of improvement... This month at least.

The 2 points on the right are fill ups after the headers. The drop in the last one could be from running 100 mph for a bit trying to get out to an emergency search and rescue. Oops. Lol

One thing with this motor that I want to mention, since it was installed, mileage has been all over the place.

These are the milage points since the 408 was installed. The highest point was an anomaly. 14 mpg holding 55 mph following a guy for about 300 miles. The lowest point was during a search with a lot of low speed driving in 4 low in the mountains of this area.

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And you are only averaging 9????? I do better than that on my 488....... (10.....)

 

I've never had good mileage with this thing, which is strange because I can usually pull the milage out of vehicles.
When it was still a 1500, 360, auto, 4x4, and 3.55 gears it got 10 to 12. After welding up the transfer case to make it a 4x2 the milage bumped up a little, but not noticeably.
After swapping over the cab and engine to the 2500 undercarriage, 5 speed, and 4.10s I had one single record run of 18 mpg. That was empty for about 150 miles, then pulling a heavy 27 foot camp trailer back the 150 miles... Through mountains at 70 MPH. Most of the return trip was in 4th gear, so I was turning around 3,000 rpms and the truck loved it. I was out pulling a stock 01 Cummins with the same undercarriage carrying a similar load.
Just before getting home on that trip some jacka.. decided to brake check me. Slip foot off throttle, get on the brakes, drop to 3rd at about 50 mph (about 3500 rpms I think), and hear something pop under the hood. Noticable loss of power afterwards. Blown plenum from the sudden suction. Truck never was right after that. Even after fixing the plenum it never had the power or milage of that first trip.
Enter the 408. Feels better than ever, but you can see variance. I dunno anymore.

 

Yeah, my 96 would average around 12 with my daily driving, and would take a heavy dive when pulling the dump trailer...... So far, the 98 seems to be right about 10, but, I have not done any pulling with it yet. That is soon to happen though. Spring seems to be actually showing up, so, time to start playing in the yard again. We'll see what happens to gas mileage with close to 12,000 pounds behind the truck.....