That pretty much sums it up.. the only difference in the firewalls is whether or not a/c or non ac. Front frames are all interchangeable, Dodge vs Plymouth. Rear frames all interchangeable between 66-70, but there are factory holes in the 66-67 frames vs 68-70 frames, in the most rear section of the rear framerails. The front cowls, upper and lower are the same, no matter if the car is a 2dr, 2dr post, or 4dr, as they are all welded, and then filled with lead, at the lower base of the A-pillar. Dodge vs Plymouth all the same on cowls. Hope this helps.
@Dodge33