I took a post 1965 fuel gage and patched around the traces/circuit board on the gauge to match the Printed Circuit Board of my '64 cluster since I have a Spectra Premium EFI tank with integrated sender/pump.
I had looked at using a slider potentiometer to adjust the resistance.
To do that, add the pot, fill the tank, adjust the pot so the gauge reads full.
Since full is adjusted and 0 Ohms is empty, then it would be accurate at full, and become "more accurate" near Empty, but sorta "iffy" in the middle.
That would be fine for a the type of driving you do.
Since I am running EFI, I try and keep above 1/2 a tank anyway. (because the Spectra uses a "bread box" baffle, and not a full ribbed baffle across the whole tank, and I have "leaned" enough the EFI Nazi says:
