Spectra fuel sending unit - my experience...
Hope it works for you.
One of the things about the sender lever position is that 1/2 travel is not 1/2 a tank.
The tank has the cutout in the top for the spare tire.
So the first 3 gallons or so go down really fast, then the tank is relatively rectangular for the next 6 to 8 gallons, then the taper at the bottom of the tank means the next 6 or so gallons goes down faster than the middle 6 to 8.
The aftermarket senders have a very linear rheostat. The OEM and gauge parts need a curve to function correctly