The fuel guage thing has always baffeled me. You have a hot wire going to a fuel source and a resistor inside that same fuel source. Duz anyone see a problem here? Electric fuel pumps in the tank bother me also. Can you say BOOM!
Well thats the way they have done it for a long time and I have never heard of one going "BOOM" so I guess its ok.
The guage and sending unit you are using --- are they origional or aftermarket?
The origional type will need a resistor or you will burn the thing out. Most of the origional guages also have what is known as a "vibrator" or "resistor" before the guage and it is usualy attached to the dash or cluster in some way. Even if you have a working vibrator you will need to drop that voltage from 12 to 6 volts before the vibrator. If not you will let the smoke out the guage.
The aftermarket type will usualy take 12 volts (see the instructions) and has a vibrator built in.
Hope this helps-- James.

I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"