Different vendors have sold me two different grommets for a '71 Charger fuel filler neck. Which is correct? The one on the right seems to essentially be the one on the left with an extra piece molded to it. It's been a long time since I took out the factory tank/grommet but I thought it looked like the one on the left. I'm dropping the tank tomorrow to replace the fuel sending unit. Even if the one on the left is technically correct, would it be better to use the one on the right? If so, should the extra rubber sealing lip go inside the tank or outside the tank?

I also posted this question at FBBO.