Stumbling after 20 miles of driving

[Test Pilot]

So I've got a problem with my truck that takes about 20 miles of highway driving to appear, once it's happens it will re-occur about every 10 miles or more frequent. It stumbles and won't pull, it rarely ever dies, but I have to pull over, if I shut it off and sit for 2-3 mins I can start it up and keep going.
Also when it does this the fuel filter is empty or near empty and no visible sign of fuel is flowing into the filter unless I shut it off as I mentioned.

Things I've done so far are;
1. Disassembled and cleaned inside of carburetor.
2. Replaced fuel filter 2-3 times just to be sure. The most recent one is a clear plastic one so I can watch for fuel flow or debris. No debris at this point
3. Pulled fuel line away from all heat sources to eliminate chances of vapor lock
4. Replaced fuel cap with new cap that is vented, or at least thats what they told me at the part store. It does have the vent valve and it does "rattle"
5. Replaced fuel pump, and all rubber line from the pump to the carb. I didn't replace the line betwee the hard line and the pump, but it's not that old and is fuel injection rated line.
I think the issue is the rubber line between the hard line coming from the cab and the steel line that runs along the frame. This look as though it could be the original line, it does have spring clamps on it that are not holding very tight as I can twist the rubber line without removing the clamps.
The line feels flimbsy.

My question is what else might I be missing? I'm going to get some fuel line tomorrow and replace it just because it's questionable.

Any ideas?
Thanks