Looks that way. Check the PN they gave you and see if it is correct for your application. I suspect (rock auto confirms) the same senders are used on a slant 6, 318, 340, and 360 (72 dart) Not to mention a slew of Fords!
One more possibility... You might have a failing ground. When you shorted the sender wire to ground did you short to the engine or to the battery or chassis?