Very nice build so far! I'm gonna be buying lots of suspension parts off you for my project in the next couple months! :D
That does not look like an AMD trunk pan. (Unless its a really old one?) the AMD ones are black and an exact replacement to the originals (has the lip in the back) and all the holes for the plugs and gas filler are pre cut and it comes with the oem style gas tank bracket/spare tire hold down. I've got one coming but it's on back order... I've seen them before so I know what they look like. It might be worth picking one up and selling yours to someone who needs to patch there's IMO. That one looks like it will take a lot to fit. (It looks like an old one that cross Canada sold out here)
You can see the lip in this pic,
I stole this pic from here someone's build. You can see the lip at the back.