gas tank filler neck issues

That is where I got confused. In the quarter panel there are five holes. It is if it was a multi fit option. I have only seen the filler necks mounted from the back side using the 4 screws. If I do mount the filler neck first by putting it through the body, I would like to be correct on what I use to fasten it on the back side. Such as the J clips that were mentioned. I do appreciate the input. If there is a pic out there for what the flange looks like from the inside of the trunk, a pic is worth a thousand words.