Installing new filler neck grommet...

1969VADart said
Boil the rubber grommet on the stove for about 10 minutes. That will soften the rubber up a lot. Then it will pop right into the gas tank. Apply some dielectric grease to the grommet once it is in the tank and the filler neck should slide right in very easy.
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That's how I did mine, put the new grommet on the tank, put the tank in place and then slid the filler right into it. Was easy both times (First time I forgot slide grommet to seal the trunk floor over the tube!)