Gonzo

I have an 89 F250 diesel with a banks turbo and 60K miles on it. Nice
truck.

Recently, I was towing 9000 lbs of trailer across the Appalachians, and
my oil pressure went from the bottom of the "low" of normal to just
above the lowest mark...way below normal. I immediately pulled to the
side and killed the engine, but the oil level was fine and the oil
looked and smelled normal and since there was nothing obvious to fix, I
finished the trip.

Once home, I replaced the oil sensor sender with a pressure gauge, and
found the oil pressure to be 30psi at cruising RPM (2500rpm) and
dropped to 10psi at idle. I changed the oil (15w40 Shell rotella
before and after the change), and the pressure went to 32psi at cruise
and 20psi at idle.

The oil pressure sensor is NOT where it was when the truck was first
manufactured, but is now part of the Banks turbo retrofit: it is
located at the end of a 1/4" oil supply tube that feeds the turbo.

So, do I have a problem? Is the pressure too low? The guy that drove
the first 40K miles on this truck used it to pull a big boat, but
nothing outside the capability of this truck. Could the oil pump be
going out? The engine runs fine, doesn't smoke, pulls strong. I've
read the procedure for replacing the oil pump, and it sounds like a big
job...any other suggestions?