I have to replace the gas tank in my 71 Dart. I purchased a Spectra tank for 72+ due to the superior vent design. My question is which filler neck grommet should I get? I've read many threads saying how some grommets are very hard to install. I know the sand/polish the filler neck nice and smooth and use lots of silicone grease but I want to be sure I'm buying a good quality grommet. Thanks guys!