That's the rear or front diff vent, that's how they are terminated from factory.
It just hangs on the frame rail , you can extend them if you do any 4X4ing or if just daily driving you just cable tie it to the frame rail (chassis)
I see some serious rust happening George?
I plan on removing the dually bed and putting a service body on. Then I can address the rust issues and probably replace brake lines.
Eventually I also have to replace the oil pan. Glow plugs, turbo pedestal, fuel lines.
I finally have the truck running right. Gauges are next.
I drive the truck everyday so I don't have time to do it all at once.