There is a test procedure in the service manual that states the readings required. It looks somewhat 3 position like (empty/half/full). I have also seen posts stating that using the factory sender is troublesome, as the float moves around with sloshing. Somehow the factory circuit dampens this.
Worth a try though. Worst case, there are plenty of aftermarket level sender kits you could use. In the end, I left the fuel gauge and the temp gauge working, and removed the tacho and speedo for a screen.