I didn't realize that the rear bumper mounts were so far out to the sides, and that rigid to the rest of the shell that they can support the weight of the car so far rearward of the rear subframe mounts. I don't know a lot about these cars, but what I do know seems to be limited to pre-74 spec. Its all about the bumpers.
I just recently became familiar with the rear of the car. I’m not an automotive engineer but the limitations of the pre-74 design are pretty apparent upon dissection.
I like the pic that @teajead posted, but Bennyz will likely be just fine. The shell is quite heavy though You can pick up the front of the shell by hand but the back weighs a lot. Doing the math in my head, I would guess that the whole shell weighs about 900lbs. That is based off of me sending 480lbs to the scrap yard.
There is no e9 rear “frame rail”. The whole back end is flimsy sheet metal. The rear wheel arches serve as the frame. Particularly the tubular structure at the crest of the arch. They are quite stout. If you look at the 74, they moved the bumper points inline with the arches, and made a shark fin that goes from the arch to the tail light (visible inside the trunk).
Here is a pre-74 (Thanks Sven). The bumper mount is directly below the tail. They won’t survive the tiniest collision. See that there is basically just sheet metal back there. A small piece of angle iron that braces the thin rear sheet metal to the thin floor sheet metal. The last thing to note is the tubular structure above the arch. The wheel arch is where all of the strength is at, and they played off that with the US ‘74: