Fuel gauge/ sending unit problem

[easyrider]

I wanted to run this by you. I ran out of gas in my 72 pickup and saw the filter was empty. Put gas in truck and it cranked back up, but gauge showed 1/2 tank, so I knew that the fuel gauge wasn't working. So, I put in a new sending unit and nothing; then I put in a new gauge and still nothing. I took the sending unit out of the tank and as I moved the float, the gauge went up and down. So, I know that they are communicating, but once it was put back into the tank it sat at 3/4 tank on gauge. I looked at an old service manual and it all looks wired right. I'm thinking that it may be hitting something inside the tank, but I have no idea what to do to fix it. Any suggestions???