If you checked the gauges then I'd have to agree with Niles that the sending unit would be suspect. IF they were electric gauges. If they were mechanical then it could be an obstruction. If its not an indication problem ie the gauges check OK then I'd suspect the end play gap on the
oil pump gears was incorrect. I don't know how the Dodge pump is set up but my Buick Grand National has the same kind of pump where its in the front cover. My buddy is a Chevy guy who checked his Grand National's pump and measured it like you do a Small block ie the gears are countersunk EXCEPT on the Buick they stick out of the housing. When he started his engine
oil pressure was fine. As soon as the
oil began to heat up the pressure would go into the toilet. He pulled the motor checked EVERYTHING including the pump. Again he checked it like a small block Chevy which he has built MANY. Again Motor back in car start it and the same thing. Could cause insanity. Finally sat down and looked at the BUICK manual and about crapped when he read how to check the gear end play. Uggghhh...
Wrong filter could do it, also an obstruction in the oil cooler.
On a different note I couldn't agree more with Niles about not trusting any one gauge. On any airliner if you get low oil pressure there is also a light. It should come on at the redline. Also Oil temp will begin to rise if the pressure really starts to go away. But its simpler in a large jet you can simply shut down an engine as a precaution (but not because of one gauge indication) on the DC10 or 747 its really a non event.
Regards,