Started running rough, backfiring, would not stay running and now it will start and run for a few seconds but will not accelerate, if it will start at all. sounds like a lack of fuel but unsure of where to start and I don’t see an inline filter anywhere on it.
Take a look at YouTube videos for the filter replacement. Even if it doesn’t solve your problem, it sounds like it is past due for a change.
Another problem on these is the gas filler tube cracking. You might have gotten water in your gas. Aftermarket filler tubes don’t last very long.
Tell us which engine you have, and what check-engine codes.
If the truck has the six cylinder engine, see if the timing chain jumped time.
Tester