Hey Felix, excellent how to mate and pretty much what I do to a fuel gauge. One suggestion is while you have it apart give the case a clean and repaint along with the bezel. Instead of the earth wire inside the housing I tin the inside of the case and the brass flap on the gauge for a good earth contact and originality, also tin the middle of the back of the case and the end of the bracket spring. If you just sand it back to bare metal it won't be long before it is rusting again and earthing problems will start again.
How did you come to those resistance values.
I get a constant 34 to 36 ohms in this instance and the four Nos gauges I have are a constant 35 to 35.6 ohms.
Stewart Warner gauges register around 44 ohms.
The four Nos gauges I have all register between 48 to 51 ohms in this instance and my restored ones generally register
between 44 and 50 ohms.