Could be fuel pump or fuel pump relay
On a 1988 there will be an OBD1 connector in engine bay, on the main wiring harness on passenger side just before it goes into the firewall to the computer
Locate it, it may still have a cap on it that has "EEC" on it
Then look here:
https://www.therangerstation.com/tech/testing-eec-iv-equipped-engines/
In the drawing of the OBD1 plug the Fuel Pump Slot is labelled
Turn on the key
Use a jumper wire in that slot and GROUND the other end of the jumper wire, this grounds the Fuel pump relay, relay should "click" each time you ground it, Fuel pump relay is GREEN, on inner fender
And that send 12v to fuel pumps, there are two
If relay "clicks" then its OK
You can leave jumper grounded and then go under the truck to see if you can hear either the pump in the tank or the pump in the frame rail(you described) running, both failing at the same time would be long odds
If the pump in the tank is running then yes, replace the high pressure pump in the frame rail
Both pumps share the same 12volt wire
If neither are running then you have a bad wire, fusible link or inertia switch
High pressure pumps, needed for fuel injection, have no suction, they can not pull fuel out of a gas tank like the old mechanical pumps could
So as a temporary measure, 1986 to 1988, Ford used a "lift" pump" in the gas tank to feed the high pressure pump fuel
In 1989 Rangers got high pressure pump in the gas tank, also different fuel gauge system