First, any sending unit you use needs to be for an '88 or older model, Ford changed the way the OHMs are used in '89, so your gauge won't work with '89 and up sending units.
73-10 Ohms, pre-1989 Fords
16-158 Ohms, most '89-up Fords
So they are reversed
Good read here on rebuilding or replacing older sending unit with a universal type:
Fuel Tank Sending Unit Tech - FORDification.com