If I had that Tempest today, I'd strongly consider getting the IRS cradle out of an Aztek or Rendezvous. Modern day geometry, my Aztek handles remarkably well and its rear end (that big glass hatchback is super heavy) is pretty similar to what my Tempest wagon had going on in back. I think I could put the original transaxle in there, the widths of it and the Aztek third member aren't very different. Then a front disc brake conversion and collapsible steering column and shoulder belts would net me a modern day, even somewhat crashworthy, one-off Tempest. A guy can dream.
Apologies for the thread-jacking daydream. I'll now return to thoughts of my big bolt school bus :-)