To clarify, the driver's mount is one piece but is not solid--the center bolt is suspended in the mount in webbed rubber. In high power cars with sticky tires, that may cause some wheelhop. That said, I think an insert would probably be a more cost effective solution than an entire replacement mount. Or you could go old school and fill the voids with 3M Window-Weld.
Correct, the driver mount/transaxle mount is not fully solid, it houses rubber.


A bit hard to see because the pics were not intended to focus on the mount. However, you can see the rubber and bolt that run through it.

