Gas gauge bouncing

[beetle1960]

I appologize if this has been discussed here before, I did a search but did not get a clear answer.

My fuel gauge on my 70 c10 bounces like crazy when moving, like half the gauge swing crazy, thought it was ground issue so I ran a ground wire from sending unit to the body, no change. I then purchased a new sending unit from LMC, no change. I have had many older vehicles (got my license in 1976) and I don't ever remember this being "just the way it is" with older vehicles. thoughts?