According to Ford, at idle, those trucks can have as little as 5-15lbs pressure, and be fine. Get a manual oil pressure tester, and see what you actually have, before condemning anything. I do believe the oil pan can come off of those in the truck. Always do a mechanical test first though. Also, Ford is notoriou for having really vague gauge readings. Althogh it shows low on the scale, it could actually be in the 40psi range, especially on a truck that's more than 17 years old.