Lets say you have actually established (with a mechanical gauge) that you have unacceptably low oil pressure. There are two different things at work. First, you could replace the oil pump, which means on a 2.6, dropping the oil pan and the front cover, removing and replacing the timing chain then the balance shaft chain and replacing the associated components along the way. It's a fairly involved repair.

Secondly, the oil pressure could be low due to worn bearings, either main or cam or both. That means a total tear down rebuild.

Thought you were going to sell the truck?

John B.