1968 dart convertible frame install

You might still have marking/scars where the large bolts in quarter panels were. That would get you close to square with the body and side glasses. The header section of the frame is attached with 2 or 3 bolts ( I forget ) in slotted holes on each side. These may be rusted. One of mine was broken off in the hole when I got there. I'm guessing a body tech attempted to fine tune away a wind noise or water leak there after the car was wrecked in that side. There was a hole rusted through the header skin so that may have been what he was after.
I wouldn't put any interior in it but the drivers seat until I took it out and tested for wind noise and water leaks. There are adjustment points to get it as good as OEM. Good luck with it.