Fuel Gauge Problem

So about a year ago i noticed my fuel gauge was not working right. when i was stopped at a stoplight it would slowly bob down to E. when i drove at a constant speed at about 2-3 rpms, it would slowly come back up to read normal. finally it just crapped out and didnt work at all. after a while of using my trip meter to know how full my gas tank was, i replaced the fuel sending unit a couple months ago. It was a little complicated:

so the two tubes coming off the top: they are different lengths, and they are different thicknesses. I don't know if it has anything to do with it, but on the new sending unit, the two tubes off the top were switched. basically my stepdad and i made it work. cut a new piece of tube for the one that didnt fit anymore, made it work. so we finished the job, put the tank back in place, filled it back up, and test ran it.

truck ran perfectly, but the gas gauge is STILL BROKEN. but... broken in a different way. now when i fill it up, it slowly rises to about half tank, and basically reads a full tank of gas as 1/2 tank on the gauge. so i fixed SOMETHING, but it's still not reading full. ever.

How can i fix it? or is it just easier to leave it alone and continue to use my trip meter as reference?

thanks and sorry for so much reading

Strange that it works in correlation with your engine RPMs. It sounds like you might have a short somewhere in your gauge cluster, you might want to try to take it out and see if there is anything there that you can clean up. I would say for sure that you have a wire loose, broken/frayed, or reconnected someplace incorrectly. Also try following the wire harness from your fuel tank along the firewall.
For the fuel lines on the sending unit, the thicker one is the supply for the engine, and the smaller one is for the return.

alright, thanks i'll check it out. that was my next step, to check the wiring. the one that connects to the sending unit was clean, and the wires i could see were intact. but ill definitely check that thanks :)