I have a 85 hatchback, when I bought the car the guy took everything off a 87 and put it on the 85, but he cant remember if he changer the fuel tank or sender. Does anyone know if these are the same, and the empty and full ohm readings. I am installing an after market gauge, call me lazy but I didnt want to drop the tank twice.

They are different if you're using the 85 cluster and wiring. If you've changed your dash and wiring to an 87+ then it will work fine. Is the car EFI or carburated?
SS

It did have the 87 cluster but he couldnt remember if he changed the sender but none of the gauges worked. I have fabracated a panel using auto meter gauges but the fuel gauge doesnt work very well, and the placement of the sender I installed "floats" too much so I was going to replace the gauge and use the original sender hoping for more accurate readings and less floating. I will just to stop being lazy and drop the tank and measure it with a meter

The 85 carb tank is different, the 86+ tank has two holes; one for the fuel level sender and one for the fuel pump. The 85 unit has one hole, where the fuel level sender is and where there is a pickup for the fuel. It does not have an intank pump unless the car is a CFI originally (which means auto and 5.0 from the factory). If your tank has two separate units in it, then that means it is an 86+. You might have an 86 sending unit which is different. Get a new or used 87+ fuel level sending unit and you shoud be fine.
SS

Is it carb or fuelie fuel pump