I bent the tank flanges by the rear spring hangars to clear the springs moved into the inside of the outer rear sub frame rails on my 1966 dodge Coronet Deluxe two door sedan
I used a dead blow hammer on my 1969 Dart GTS to make clearance on the rear of the passenger side gas tank on that car with the leaf springs moved into the inner side of the inner sub frames, about 3/4 inch closer to the outer fender wells with the springs that way
No problems with the front of either tank on both cars