You can run tape along one side vs the other to help get an idea on your bodyline situation. Look at some videos on youtube about doing bodywork for custom cars etc. Doesn't sound good but this needs to be diagnosed in person. Since this is a unibody damage to the 'frame' is often not 100% correctable. It can be done but involves pulling and stretching the body.
To give you an idea, last weekend I was going through a rear-ended 392 - the damage went all the way up to the end of the spare tire wheel well - visually. We ended up having to use a cutoff wheel to get the passenger side front seat track out... that's how hard it ended up tweaking the body.
I think if it were me I would pull the front clip and fenders and run measurements from boltholes/mounting points on both sides to determine if the issues were the body panels or the unibody itself, and go from there.
It may make more sense to find a donor shell and start over with your mechanicals... Sorry man.
To give you an idea, last weekend I was going through a rear-ended 392 - the damage went all the way up to the end of the spare tire wheel well - visually. We ended up having to use a cutoff wheel to get the passenger side front seat track out... that's how hard it ended up tweaking the body.
I think if it were me I would pull the front clip and fenders and run measurements from boltholes/mounting points on both sides to determine if the issues were the body panels or the unibody itself, and go from there.
It may make more sense to find a donor shell and start over with your mechanicals... Sorry man.