My sending unit had a ground wire going from the sender to the wire support screw under the driver's side of the cab. I restored that connection when I rebuilt the sending unit harness. So Chevy recognized the problem back in 1951.
I had a very original '52 that came wired just like that. A real head scratcher. Why would the sheet metal on the underside of the cab exposed to the environment be a better ground than the sheet metal at the cab support brace above the sending unit? An additional aspect of the original sending unit ground wire is the additional cost for each truck produced for that long copper wire.
