Fuel fill tube

I have a 68 and a 70 tube but both have rust inside. Have the original 72 tube and you are correct. Is longer and different flange.
I understand the original tanks are the same except vent on the tank. But the repro 70 tanks is not a correct 70 tank.
I'm not concern about it being correct. I mainly wanted the earlier 18 gal tank versa the 71 and up 16 gal tank.