I can not take credit for this. This information was sent to me by challenger6pak. This info was a big help for me. I would lube up the tank gasket a little with a tiny bit of Vaseline.
Let the tank drop down some. I take the passenger side tank strap off and leave the drivers side loose. You will need someone to hold the tank if you take the passenger side strap off. Put the tube seal on the tank. Put the trunk floor seal on the tube. Bring the tube through the floor and into the tank. Bring the tank back up into place. Be careful the tube does not wedge itself against the inside of the quarter panel while raising the tank. It could cause a dent. Line up the filler neck to the inside of the quarter. Put foam seal between quarter and filler neck. Screw the flip to cap on with the gasket on the outside under the trim ring. The flip top screws go through the quarter and into the filler neck. Lastly attach the trunk floor filler neck gasket.
Trivia: Do you know why Dodge designers put the filler neck on the passenger side? It was to keep people safe if they ran out of gas and had to refill along the road.