Here is another little update:
After getting the new rear frame rails build and the 4-link mocked up, it was time to tie the whole thing together.
Here is where we cut out the existing rails and part of the floor to make room for the new rear frame and the subframe connectors we fabricated.
As I mentioned, we built some subframe connectors:
But they did not work out, so it was a lot of wasted effort. I just am showing them here, since I may as well get something out of all that effort, right? Anyways, we ended up going with a plain piece of square tubing for the connecting section after these did not work out.