Wiring cluster go to the fuel sender unit wiring diagram needed?

None of them. The level sender goes to the PCM where it is turned into digital data that is sent to the dash through the data buss. The same is true for all of the gauges on the dash. They go into the PCM and are then sent to the dash module as data. What is the issue with your fuel gauge?

Okay, if the gauge test is good but no gauge it can be either the ground or the signal wire. I would do a simple test. Take a simple test light, unplug the fuel sending unit harness and get it to where you can access it, find the 2 pins that carry the signal to the PCM. Now connect the test light to a good ground and touch the tip to pin 3 (dark blue wire) with the key on and watch the fuel gauge. If the wire is good to the PCM the gauge will move to one side. If that works then connect the test light to battery positive and then touch the tip to pin 1 (black wire, light should light) now touch pin 2 (black with blue stripe) that is the signal ground, and the light should also light up. One or the other should show up as the problem.

Sounds like a bad ground as you discovered. You can leave it but it could cause issues by drawing extra power through the sending unit.