Assuming the sender is good I would either suspect a wiring issue with the 5 volt reference from the PCM, a wiring issue with the signal wire to the PCM, a problem within the IPC, or a wiring issue to the IPC. I suspect you put the tank back up or put the bed back on but checking for the problem at the fuel pump connector is best. You can check your 5 volt reference from the PCM at the fuel pump connectors purple wire. With connector disconnected you should have 5VDC with the key on. If you have 5VDC the PCM reference and wiring to pump connector is good on purple wire. With a paper clip you can check the reference signal to PCM by jumping the purple terminal to the signal wire with the key off. Im sorry but I do not know the color of the signal wire but I believe it's black. Then once jumpered turn the key on. Gas gauge should go to full. This will narrow down your problem to the signal wire, PCM issue with signal, or wiring to IPC. From there you will have to check resistance on wires for shortsor breaks.