Gas gauge issues
 

Hello, I posted earlier but couldn't find so I'll try again. I just got a 67 cutlass, through the years and what not it ended up with a 68 olds 350. Engine runs great, my issues are mainly the gas gauge and most of the dash cluster is dead. I haven't tracked down the Speedo cable yet. The gas gauge needle raises a little above full when the ignition is on. I get mixed info on what that means. Some say that's the result in a bad ground at the tank and others say gauge, or sending unit. I'm pretty good with a wrench but I have no experience with troubleshooting this issue. Any info would be greatly appreciated. Thanks in advance,
Tim