A few months ago I posted about testing the gauge and sending unit. After pulling sending unit from top of tank (access hole in floor) and after removing 1 wire hot lead , the cork floats were found to be saturated thereby causing empty reading at gauge.
I had a couple of gas resistant neoprene or nitrile Model A Ford floats which fit perfectly and are readily available. The sender takes 2.
A wire to chassis from one of the sender mounting screws was added and insured better ground than just the sender flange.
Fortunately the gauge is fine and has no flutter
Hope this is helpful to others.
Thank you, Lew. Reports like this are always useful to someone.