Don't know about the '89s, but the '88s had two fuel pumps. They had a low pressure pump in the tank feeding a high pressure pump mounted on the frame rail under the driver's seat. Went through 2 high pressure pumps before I realized the low pressure pump was causing them to fail (it ran fine without the tank pump, just kept burning the other pump up.)
In the 80,000 miles I had mine (bought it at 75,000 miles), I went through the fuel pumps, a couple of alternators, had to convert the A/C to 134 when the compressor went out, several back window switches, and a set of window switches in the driver's door.
I'd still own it today, except the towing capacity just wasn't enough for what I was trying to do. I replaced it with an F250, and wish I had had the money and a place to park it to just keep it.