On most all fuel tanks, the sender will always read less fuel between empty & half, than half to full. It gives a false sense of mileage. You seem to be able to drive many miles before the needle even begins to move off of full. The resistance change of the fuel sender is not consistent throughout its range.
I'm guessing a true half of tank will be shown with the needle between 1/2 & 3/4. Paul.

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'84 300CD 290,000