Door alignment

[67 ls1 vert]

Hello, I have a 67 Camaro that the rear of the door sticks out a little. My friends car does the same thing. After we noticed that both of our cars do the same thing, we started to look at others and noticed that its like that on other cars also. Not all, but some. Any idea's how to fix it? The rest of the door look straight , its only the back lower corner that sticks out.

Thanks.