Just keep the Prothanes in the two mounts that resist the (apparently massive) torque of the motor.
If you have a "big liquid filled" mount like we do on the B13, just return that one stock. That is the one transmitting the vast majority of the buzz to the cabin.
Dave Coleman, SCC, waaaay back in the day...blah, blah, blah. Did all four (4) with ES inserts, deemed it too buzzy for DD. Switched the "big liquid filled mount" back to Nissan stock. Concluded as excellent compromise.
Congrats on the birth of your adorable new-born big-block.