Does anyone have a diagram or picture of the rear axel of a 1983 f150 5.8 liter 4x4? I have a hose hanging (which I think goes to the rear tank) and would like to know where it goes.

 

You need a picture of the rear axle or rear tank?

 

Might also be the rear axle vent tube. That would connect to the top side on the drivers side, about midway between the pumpkin and leafspring. I found mine to be dry rotted and broken in half after 25 years. Not sure if it is what's hanging loose on your truck, but it is a possibility.

 

I'll bet it's the vent 86ford is talking about above. It just gets clipped up there someplace, should attach to the axle where the brake lines converge.

Here is a picture showing the brass nipple, the actual vent tube is to the left:

 

There shouldnt be a return line to the fuel tank. The old carb set ups just dead head.