I don't know how much trouble it is on your truck but I would be inclined to drop the pan and check the pick-up screen for blockage.

 

I'd be inclined to check the main and rod bearings while in there and replace the oil pump, doing a timing job with new tensioners and guides in the process.
You are right, it probably has a clogged oil pump pickup tube from silicone pan gasket material and timing chain guide plastic