A different fuel gage grounding problem

[Tucson38]

I know this topic has been done to death but here's a twist. I have the usual
"fuel gage @ the 3 o'clock position" indicating a ground fault but…..it does it with both tanks. So my assumption is the ground fault isn't at the tank as usual so is there a place for a common ground for both tanks? Perhaps at the gage itself?

Thanks for any help.

'85 GMC 3/4 Ton HD 4 WD