The stepper motor will not trigger the light--
The problem is the fuel sender-- or the wire to the sender. Remove the connection at the sender-- the fuel gauge should swing all the way past full. If you ground the wire, it should go to empty. If it does this-- you need a tank unit. They are $$$.
If you are handy, you can find this-- and just replace the resistor part--Dorman 911-005. It only costs abt $30, and you fit it in your tank unit. Dorman has made auto parts since abt 1930. Google found it-- Amazon-- Summit-- and some auto parts stores.
Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.