Zero means NO oil pressure. If this was truly the case, your engine should be making noise. Replace the oil pressure sensor. Right above the oil filter on a 4.7L.

 

Testing with mechanical gauge and replacing sensors are both excellent suggestions.
Other possibilities; oil pickup tube is clogged, oil pump is clogged or failing.
I would need to see what the top of the head looks like; is everything clean up top, or, is there sludge?
I'd rec more checks before going rebuild route.
Did you buy truck like this, or have you had it for a while?

 

Auto parts store will rent a pressure tester for for free, once you return it.

 

For what its worth I replaced the sensor on mine with no change in readings.

I don't believe the truck actually has 0 pressure. It drops from the low end of the gauges to 0 to fast and never reads in-between my assumption is its the sensor is more and on off switch then a sensor, anything below 35-40 it just reads zero. I would've long dropped out the bottom end if it was actually going to zero, as would the OP it sounds like

My 06 4.7 I did have oil pressure reading issues also and it did turn out to be the sensor. I forgot about that, I dont remember the exact symptoms, I think I just had no oil pressure all the time on the gauge

 

I've changed the sensor, changed the oil pickup tube, and put a gauge on it and it read 0 at idle when warmed up. I changed the oil a few times.

 

Not so easy to swap the oil pump, but I think I might do that before the bearings.

 

The oil sump/pick up tube is where I would look to next.