Sometimes you do. If the new fuel pump came with a substitute harness you will need to. The reason is that a change has occurred possibly due to a recall and the old harness won't fit the replacement pump.
You will need to remove the fuel pump wiring harness. Remove the fuel pump fuel lines. Remove the fuel pump retaining bolts. Reverse the process to install the new fuel pump.
The VSS is located on the top of the transmission and is connected to the engine wiring harness. To replace it all you need to do is unplug the old one from the wiring harness and unscrew it from the transmission, instalation is the reverse of removal.
The term "harness" refers to the wiring loom. The fuel pump harness would be the wiring to the fuel pump assembly. That wiring would be part of a much greater wiring loom, that would run along the frame rail, and immerge under the hood to become part of the main engine control wiring harness assembly, which includes all the wiring to all the engine sensors and solenoids, and even runs to the computer. You can locate one end of the harness where the connector plugs into the fuel pump on top of the fuel tank. It will go from there, and pretty much run the length of the car, spidering out under the hood, and going just about everywhere. There may be a connector or connectors that separate the rear body and fuel pump harness from the rest of the vehicle harnesses, but don't count on it.
You need to most likely replace your fuel pump wiring harness. It is located in the gas tank connected to the fuel pump. While your there you should also replace the pump and sock. Note the configuration of the old wiring harness when you pull it out because the new one you get is a generic one made to fit different cars. You WILL have to rewire the new harness to make it work.
get the wiring harness from the explorer or donor vehicle that you get the 4.0 from, you need the harness from the 4.0!!!
Do you want to replace all the wiring or just part? There's a company known as PAINLESS WIRING DO a google search on them, they are a leader in the wiring of autos, they can even make up a custom wiring harness if you need it. If you just need replacement wiring, maybe check the local salvage yards but that may be a tough find.
Will the bell housing mate up to the new engine? The wiring harness and computer will need to be replaced. Do both engines require the same fuel pressure, if not then you will need to replace the fuel pump. And the beat goes on.
YES, if you know what you are doing. You will need the complete engine and transmission wiring harness and computer plus the fuel pump for the 5.3L engine. The wiring harness and computer on the 97 will NOT work.
Yes
It wouldn't be impossible, but you will need to also replace the wiring harness that goes with it.
Not easily. You will need a different computer and wiring harness.
On newer fuel injected vehicles you will usually need a new wiring harness and engine computer to match the engine you are putting in. You will also need various sensors for the new engine such as mass airflow sensors and intake air temperature sensors.