Neat and all but none of that really helps the OP or explains any issue he may have.
Maybe the conversion information I mentioned was unnecessary, but my point wasn't about the conversion per se. It was about the fact that the problem that the OP is having with the trunk floor seal shouldn't be a thing. The trunk floor seal itself was the same from at least '70-74, which covers several emissions changes with regard to the tank. The hole in the trunk floor pan didn't move, the same pan is used '67-'76. The filler tube itself didn't really change either, certainly not from '70 to '71. The cap changed, but the tube was still mounted inside the trunk, the angle didn't change, and the hole in the quarter wasn't moved from '70 to '71 (same exact quarter panel was used). Or for '72 for that matter, or even '74 even though those quarters had other changes. While the filler tube was moved from inside to outside of the quarter panel and the mounting of the cap was changed, nothing else regarding the filler tube changed from '71 to '74 for the same model car. Otherwise I couldn't have used a '74 Dart filler tube on my '71 Dart without running into the same issue. And lots of people change those 1 year only filler tubes out for other model years because of the scarcity of the caps.
So my point was that even if the filler hole in the tank moved with that emissions change in '71, nothing else did. Which means the factory and everyone else was able to use the same trunk floor seal despite that change.
