New sending units are not available. I found a bad wire on mine and fixed it. I also had to solder the lines where they go through the unit. That was easy.
Might find someone that will build a bumper from scratch and save some money. The one on my ZJ cost me less than a kit and has been put through some tough tests.
Failed regulator will cause too much fuel in some vehicles. TBI Chevy would dump so much fuel that it'd dilute the oil and I have seen signs of exhaust catching
on fire.
Just for grins, with the engine idling, try moving the wiring to the ecu. The weight of the harness can pull down and crack the circuit board over time, can cause cutting out. As it gets worse, a no start condition can occur.