fuel gauge

just got my 89' back up and running, it runs great with no problems after new tank install and sending unit, due to my fuel pump going bad. Now i have only filled the tank with less than 5 gallons maybe 2.5, and my gas gauge shows just below "E" when the vehicle runs, now if i jack the vehicle up, the gauge will move just above "E" so i know its working, will i need to fill the tank up more before it actually shows it has fuel in it? i have not taken the vehicle to a gas station yet b/c its not registered, but the gauge was working before i removed the tank. I have rechecked the plug to the sending unit and it held sht w/ a zip tie in place of the white plastic clamp. Anyone with ideas, i really dont want to drop the tank again, but i will if i need to.

i would fill the tank up all the way and then see what happens