I'm so sorry.  That is really really frustrating, especially since you've really been thoughtful with the restoration.  How is insurance in this case?

Still working with them.  I'm pretty sure they are going to say its a total loss.  Gotta figure out what my options are with them.  

Did it affect the other side quarter panel? If the damage is just in that one corner I think it should be fixed instead of looking for another body. I'm not bodywork pro but I would guess easier and cheaper too. If the whole rear moved sideways then it's a different case. 

Unfortunately the other side buckled meaning the whole rear shifted and would need to be pulled back towards the passenger side. 

That's a bummer, but still I would look into option of fixing it. You've done good work restoring the body and the damage looks to be limited behind the axle. When I did my restoration I replaced both quarterpanels, trunk floor and rear clip. Surely it was a lot of work but still quite straight forward.

+1 on Tommy's comments.  At the end I don't know if you end up with a salvage title (to some that counts, others not so much).  With the frame alignment equipment they have now, they can pretty much do anything.  It is a matter of cost, but if you can find someone that works on classics you might have better luck than a 'collision shop' - best thing to gather as much info as you can, call/talk to whomever in your area that has the gear and then make an informed decision from there.  I ended up putting an entire rear clip on my race car.  Expensive? yes.  I had no choice with this particular car.  It ended up needing some pulling here and there but given how hard it was driven, is pretty straight (now).  Good luck with your car.