Probably 3 or so ohms for full and 120 or so ohms for empty. See: https://www.ply33.com/Repair/fuelsender2.html

I am having a new fuel tank made for my 32 Sport Roadster. The maker needs the resistance of the factory installed gage for compatibility with tank sending unit. Can someone tell me what the resistance is or how to test for it?
Thanks,
Ellis Smith