By any chance does anyone have any photos of true duals on a 86 F250 with the 460 and t18 4x4? I've been trying to figure out how to run mine around the dual tanks and out the rear on each side

 

You have to run both down the pass side, and then cross over at the rear to bring one out each side. LMC Truck sells a system already bent, but it's for a 302, not a 460. I ran my own homebrew system, bringing the system under the frame up front on each side, then a 90 on each side pointing up at a 45, then another 45 to level it off, and then the cat, the muffler, and then a turn out in front of each rear tire. Looking at the side of the truck you will be able to see the exhaust when it runs under the frame, but turning it up on the outside of the frame on each side brings it up and hides the rest of the system.

I think the slick way to do it would be to buy a aftermarket 38 gallon rear tank, get rid of all that fuel switching mess, and get rid of the front/side tank. Then you would have room for the exhaust on the driver's side, and get rid of the fuel system headaches also.

 

I don't have photos and my truck is an auto but
I ran mine down the passenger side as Franklin2 stated.
I have them exit in front of the rear tire because I didn't want something in my way to get to the rear tank.
I don't know about all f250's and up but mine is cat exempt so no cat is needed. The mufflers are side by side in a vertical positioning.
I don't think you could install than in the "traditional" horizontal position easily if at all.
My side tank is still installed and I also installed the 38 gallon rear tank.

 

Kept both tanks, ran long tube headers on a 351W in an 83 regular cab, both pipes down the passenger side and exited with 2 angled pipes just before the RR tire ala' Lightning. Had glasspacks squeezed into the space between the driveshaft and the frame rail, all on the left side. Was really obnoxiously loud, but I was young enough to appreciate it.

 

Ok lets think out side the box a little here. Back ground on my thinking:
I have a 300 six with 94 EFI EXH manifolds, flows better than the log exh manifold, running into a factory replacement Y pipe and 94 F150 pipes, less cat, to the factory tail pipe. I also running a Thrush welded muffler. The reason for this is the 94 pipes are larger in dia. than the 81 pipes.

So with that said I would look into diesel pipes of our year or even newer and see what size they are to our pipes.
Yes it may be a single pipe but if bigger you would not need to make up a system like you would for duals and you can get the system from any parts store.
You would need to join your factory Y pipe to the diesel larger front pipe but should not be to hard to do.

Heck if you know the factory diesel pipes will fit the truck, I dont see why not as it fits a F truck already, they make even larger pipes for aftermarket diesels up to what ? that is pretty large for a 460 gas motor.

Just something to look into that may work for you with less work.
I only needed to cut off a metal wire hanger from the tail pipe that the 94 truck used and used the 81 hangers for the full system.
Dave ----

 

2.5" dual is fine for stock 460 3" if single and if you have it hopped up than 3" above for duals depending on the HP you built it too.

 

What is the factory single for a 460?
If it is 2.5 single and a diesel is say 3" single then is may be worth going with diesel pipes and only have to deal with adapting the small Y pipe to the larger diesel pipe.
Other than a cat on the newer diesels I dont really see why that system would not work also as what all has changed between the trucks under sides?
Dave ----

edit
I did a little looking and for 85 F250 460 & 6.9 only the tail pipe was different that I could see, diesel was 2.5" / gas 2.25"
Front pipes were 2.5 for both 460 & 6.9
I then looked at 2000 F250 SD and we then got 3" pipes and tail pipe. I also saw a 4" pipe but dont remember if there was a tail pipe to match?
The only thing I did see was a wide frame or not? Guess pick up or CC? But that may be for off set front / mid pipes between the trucks?
So 2000 F250 SD could get 3" factory pipes and be larger than the 460 2.5" front and 2.25" tail pipe.

 

I don't recall but I think it is 2.25"

 

As you found out the early diesel's did not have 3 inch pipes. Mine has a fairly normal sized exhaust system. But they were not turbo ed originally either.

 

On my 6.2 Blazer it had duals and think the pipe was 2.5 also non-turbo.
Now when I installed the Gale Banks turbo they swap out the exh to a single 3"
When I first pulled the 3" pipes out of the box they were huge!
That turbo was the best thing I did to that truck, made it like a big block gas truck but the MPG of the diesel.
Dave ----