Another fuel tank leak question

[SBpunk]

So dropped my fuel tank to fix my sending unit. Now I can't get a good seal on the sending unit. There is a small rubber piece that presses into a hole at the bottom of the tank and I'm wondering how important it is. I can get a good seal without it but having issues getting it pressed in with it on. 

[SBpunk]

^{Ok got it figured out so far. Put some vasoline around the rubber cone and the o-ring. Seemed to seal up nicely and now I can tell that I'm out of gas......}

[SBpunk]

So go the fuel pump in and still just hanging under 1/4 tank. Manually moving it registers on the dash but no luck while it's in the tank. Any ideas?

[64 Cheyenne]

Adjust the float arm?