I've been a Fabricator for 35 years but not a Body man
I have a 1956 chevy truck I am restoring.
How to fix??
The door panel is not flat in some areas and need to be body work back flat, see Video link
There is a brace about mid way down the door on the inside but NOT touching the panel and it is bent.
I could make several braces to put behind the panel and pull it back, But I THINK it needs to be split with a cutoff wheel first??
You can buy door skins for 500.00 + shipping and they may or may not be flat, most of the aftermarket panels don't fit and have to be modified, so I want to use what I have.
I just made this Youtube so it may not be loaded yet
The gap is about 1/4" on the left and 3/16" on the other

https://www.youtube.com/watch?v=sswGR5xr1c0