I used my free 1 1/2-inch muffler tubing to put the neck back on. I cut the angle to make it fit vertical. It's kind of an eyeball thing, so don't make it more complicated than it is. The overall height can be trimmed so you can have room to put the rubber filler hose and clamps between the bed and the tank. When you weld the neck back on, don't forget to put in a vent tube. I sealed the welds with JB Weld to make sure I closed up any pinholes and to make the welds look as smooth as possible.