Hi Ronzara. I'm running SW gauges...and I have to agree with DScott. You have the same problem I had......the gauge pind to Full...and the tank was empty....you got the wrong fuel tank sender. I had the right sender for my gauge so I just had to remove the tank....and then modify the sender....since yours is a EM...you might have no problem in just changing the sender for the right one....but for me the CR Cobra tank was alot more difficuilt to do, since it is attached to the whole mounting section for the return and emissions lines for the tank.
If you don't have any numbers on the gauge. Some of the SW gauges have it indicated in the face of the gauge at the bottom...just under the needle...or call who ever you bought it from and, ask them what the ohms are for that gauge....or ask them to send you the right sending unit for it. I'm sure DScott is right.....it's the sender unit.
Did you buy the gauges from SW....is this the gauge set?
http://www.xks.com/SW%20Pages/swgaug13.html
If so, it says the SW-82303 Fuel Level, 240 OHMS or the
SW-82413 Fuel Level, 240 OHM. In any case there both 240 OHMS.
Snake.