FUEL TANK INSTALLATION ORDER

1970 gas tanks are wrong. I been down this road before. They advertise the tank as a 68 through 70 but that’s incorrect. 1970 is actually a one year only tank. You need a 72 tank and plug the nipple on the top of the tank. The filler hole in the tank is in a different area.
Ah crap. That's what I get for buying **** too far in advance. If the 70 and 71 cars have the same quarters, and I am using the 70 filler pipe why does it not work? And, why would it work on a 1970 car then? Trying to understand. I appreciate your input.

And......Would I still be able to use the 1970 filler neck with the '72 tank?