the427chevy

ok so, after a longgg fight with this machine, had a rusted out sending unit, fuel gauge was pegged all the way up, new tank, sending unit, and lines, gauge was still pegged, took the cluster apart, everything under .05 ohms resistance, ohm'd out the chassis wire from the sending unit to the gauge, couldn't get a constant reading, and it wasn't what the sending unit was ohming out at, so i ran my own wire from the sending unit to the back of the cluster harness, gauge now works but is very bouncy, anything i can do to make this stop, or is it the sending unit?.... i've heard about antislosh modules? curious what my options are