70-71 AMD Fender fitment woes

Get a large contour gauge and push it on the door for a pattern. You can use a piece of cardboard hold it to the front of the door and run a marker down the edge. Cut it out and you have the door contour. Fasten the fender at the back top and bottom to a ridgid fixture. Use a porta power wedge with wood spacer and spread the fender from the fixture until it matches the contour of the door.

I am having issues with door gaps at the top of Demon quarters from AMD. But they are the best we have to work with for these 50 year old cars. So I have to add metal to the door.

If that fender was side swiped years ago and flattened slightly we would have pushed it an fixed it. Its called collision body work.
After reading this, I would agree with the porta power trick over what I had suggested earlier. Funny thing is that I would have probably thought of that if I was actually working on it. One of those thin spreader type heads would most likely do the trick of getting it close.
I also agree that body work is required on these parts. It's pretty common not only on metal reproduction parts but also on fiberglass parts. I built a Factory Five 65 Cobra (they have revised the body a couple times since) and I swear they pulled the mold off of an actual Cobra which had poorly repaired collision repairs done to it. I must have spent 2 weeks or more fixing the fender and driver door as well as a couple other areas and it all looked like the result of a collision.