Ends up the car mounts aren't tall enough to work
so I am forced back to the now $150 per corner mounts.
A bit more digging and I find out that our mounts were made by isoflex for diecon engineering and look identical to isoflex mounts.
Turns out isoflex mounts (and polyflex) are rebuildable and new centre cores should be considerably less than new mounts.
Fingers crossed for Monday when they get back to me.