'66 Barracuda gas filler/tank

65ChargerDart said

There's a rubber grommet that fits in the hole in the gas tank the filler tube fits through, and seals the opening.
On a Dart, there's a metal plate bonded with a rubber covering where the tube goes through the floor that seals it. They are available from DMT:
Mopar A Body 63-66 Barracuda Dart Fuel Filler Tube to Trunk Floor Seal

Click to expand...

Fortunately I have the part you mention & have the grommet and new tank/strap/sending unit on order. I was trying to figure out how to wrestle the filler neck loose (out?) to get it in the right position to attach the rubber hose & line up the chrome sleeve. Maybe I don't need to get it out, but it seems awkward as hell to deal with. I'm gettin' too old for this. :)