Dashboard voltage limiter?

If your temp gauge works, the IVR part of the circuit should be OK. So now concentrate on "the path" from there to the sender. Examine the board trace from the IVR to the fuel gauge stud for any breaks, and "ohm" it out IE check for continuity. Loosen/ tighten the gauge nuts about 3 times to 'scrub' the connections. "Rig" the cluster to 12V and ground, and ground the sender wire of the fuel gauge to see if it moves. Watch it and do not ground it longer than necessary to get a reading.

If that works, check the wire from front to rear, and as others have mentioned, concentrate on the fuel sender ground. Devise a way to clamp a ground pigtail to the sender outlet nipple and ground to the body.