FYI....
Had a set of front mounts bolted to a 351w (mock up engine for test fitting).
Sitting there having a refreshment , thought: looks like if I take the one from the front left, it should work on the back right.
I'll (one day) drop the engine in the car to see where they match up with the frame rail.
If it fits OK, will be a good way to mount the engine.
I held a set of Headman Headers up to the ports. Fits OK.