Okay guys, here we go. But before we get started, this set up can be done much cleaner in my opinion. So forgive me for the crappy example.
The OP was asking where he mounted the ring at the back of the truck. I actually welded a piece of strap to the chassis, drilled a hole through it for the solid fuel line, and tach welded the line in place.
Next, the question was how to keep the cable from coming all the way out the hard line for the air shut off. A cable clamp before the hard line at the blast gate keeps it from coming out of the hard line, and zip ties on the ring at the back of the truck take care of that. The cable clamp hits the hard line, and the zip ties break. Cable stays in the hard line.
NOW, since I pull with more than one organization, I have to have 2 ways to pull the air shut off. In cab, and at the back of the truck. But I also have fuel shut off at the back of the truck as well as you will see in the pics.
SO, for in cab I got a sheathed hard cable with a "pull to stop" handle on the end from Tractor Supply. This cable is 6ft long with a soft plastic cover. I routed this from the dash to the blast gate and trimmed the hard cable where there is only about 3 inches from the end of the plastic left. After I mounted my hard line for the cable to the rear, I attached the cable to the plastic of the in cab shut off with zip ties, and cable clamps. So now if you pull on the rear cable, it will pull the plastic of the in cab cable, and pull the hard cable out of the blast gate. It won't come out of the cab since there is a knob on the other end not allowing it to be pulled out. AND, my cluster f*** connection there makes the knot that won't go through the hard line. LOL
Okay pics. Here you can see the over all set up. I have the hard line for the rear cable bolted to the master cylinder, and bent over towards the turbo. And you can also see the plastic sheeting over the in cab hard cable.
Next is a better pic of my "knot" LOL I attached the rear cable to the in cab hard cable with cable clamps and zip ties. Don't clamp too tight, or the in cab cable will bind up.
Next a closer look where you can see the end of the in cab hard cable going through the blast gate.
Here at the back of the truck you can see where I have both my air, and fuel shut offs. The air shut off is actually tucked back because the last pull required fuel shut off at the back, and not air. But this pic shows the location of mine answering the OP's question.
This last pic shows how to mount the 2" steel ring to your cable. Just 2 zip ties. The shut off with the ring on it in this pic is my fuel. but the cable that is tucked back has a ring mounted exactly the same way. And you can see how I ended my hard line for the air shut off cable.
I hope this answers everybody's questions. If there is something I missed, or that you want to see something else, just let me know.