It always starts right back up and drives fine at 40 mph but once pushed closer to 60
The engine quits, or the whole truck shuts down? Is it a Diesel? How old?
We can give better answers if you ask better questions…
Yeah not a whole lot to go on but first thing I’d do is hook up a fuel pressure tester and tape it to the windshield. See if the pressure is up to snuff and if it falls off just before stalling at 60. Once you can determine if it is fuel or spark, you have gotten closer to a solution. Nice part is that it happens all the time.
A partially plugged catalytic converter can cause this symptom too. Diagnostic engine codes is where to start.