Well, I was wrong too. I forgot about the IRS on the Tempest.
Slight hijack: Solid rear axles are sometimes refered to as “Live Axles”. I wonder if the term “Live Axle” originated to indicate that the rear wheels were not driven by chains as in the very early cars? In which case IRS would also be a “Live Axle”?
I don’t know the orignin of the term, but in the auto repair field “live axle” refers only to solid axles, which preclude IRS.