fuel gauge problem..

I swapped an si cluster in my 94 dx because I needed a tach after the engine swap..
Since then the fuel gauge has been way off. when the gauge says
I got a quarter tank left I was stranded on the side of the road out of gas. when I have three quarters it says my tank is full..
is their a way to calibrate the floater in the tank?? or is it a sensor that you can't calibrate??
about to replace my fuel pump and this would be a great time to fix the gauge issue sawell if it can be done.
thx for any info..