Since hes just replaced the gp's and uvch and pigs tails, that would be the first place i'd check. Ohm out the glowplugs and double check connections. Did you only do the pass. side GPs?
Test the GPR. Use a DVOM set on DC Voltage
1. With the Key Off
2. Negative lead on the negative battery post.
3. Positive Lead on Terminal 1 in the picture. (Should read 11-13V)
4. Now Place the Positive Lead on Terminal 2. (Shouldnt Read At all)
5. Now turn the truck in the run position.
6. With the Negative lead still on the battery, Repeat steps 3 and 4.
When you place the positive lead onto Terminal 2 though, you should get a reading. (11-13V)
If you dont, your GPR is bad.
I re-read you post and I guess I missed the part about the truck running and dying (Its 12:30 here...)
That doesnt sound like a bad GPR (Though its a good idea to check it and it takes about 2 minutes to do so).
But, Its probably going to be a 'how many parts can you throw at this thing' until you get a quality scan tool hooked up.
Any power loss when it was running before dying? Long periods of cranking while trying to re-start? Did it shut off all of a sudden or was it sputtering/hiccuping?
Check your ICP on the drivers side head. Unplug it. Is there oil in the connectors? See if it starts. This will set off a P2285 I believe, ignore it.
If the truck starts, ICP is bad.
Take the oil fill cap off the passenger side valve cover. Take a good whiff of it. Does it smell like oil or burning plastic?
Burning plastic would point to a bad UVCH. Though these normally wouldn't cause no-starts.
Check the 'tin nut' on the back of the IPR, though I dont think this would cause no-starts. I Could be wrong.
Im just thinking out loud here.