33 ford Vicky gas gauge needle jumps around

[Rickmo]

I have recently purchased a 33 ford Vicky that needs some work. It's a kit car so no parts are original. I noticed that while driving the gas gauge needle jumps around so until I come to a stop I have no idea how much gas I have left in the tank. Before I drop the fuel tank to investigate the sending unit, does anyone have any thoughts what the cause or causes maybe? Thanks