70 duster gas filler neck.

I need a gas filler neck for a 1970 duster.
The recess in the body has 3 holes.
I bought a gas cap for a 70 duster & it doesn't fit, then I noticed the filler neck has 4 holes so it must be from a newer model. The gas cap that was on it isn't flush with the body so I thought it was just the wrong cap.