gas tank sending unit

78 ohms or greater = no needle movement. 73 ohms is up to the first "empty" hash mark. Should we consider that approx. 3 gallons of reserve/insurance/cushion ? In any case, what you state is too typical. Lets first prove you car does still have its OEM sender. If so, you could install any aftermarket sender at any price and see if there is a change. I'm betting against it.