It seems that you guys are forgetting the 1970/71 vent tube. In my 70, there is another pipe just behind the right rear wheelwell inside the trunk. 4 lines go from the gas tank UNDER the car into this tube, with a 5th one that runs out and forward to the engine compartment. This tube in the trunk is the same galvanized type and diameter as the filler tube. I seem to recall that this was an emissions thing that was later changed. I have seen this in A body cars in 1970 and 71 as well.