I put a few gallons of unleaded in a diesel truck (2008 superduty) then immediately filled it with diesel. It runs fine. I hear a few gallons won’t harm the engine
Your truck has a very large tank; just keep it topped up with diesel.
It will not do it any good and in some trucks and cars the gasoline can damage some rubber parts as well as cause additional wear on other parts.
It is certainly not a good thing to do, but hopefully it will not cause any short term or long term problems. There is no way of being sure, but chances are in your favor. Good Luck.
As long as it’s as diluted as possible, it shouldn’t be a big deal. Fill it back up with diesel at half a tank; if everything’s good at that point you should be okay.
Just don’t do it again. 