That's the common SBC motor mount. Energy Suspension products makes a polyurethane mount that is far superior to the rubber mount. I'm not a fan of solid mounts for street vehicles as the flexible mounts really do dampen loads to the chassis making for IMO more pleasurable ride and less stress on the chassis in general. I would think this would especially be the case for a V8 in a Datsun chassis.

Regards, Kitz