Have you driven your car without the body/xmember mount and it's vibrates too much for you?
The properly tuned V8 revs smoothly.
I originally had more "isolation" in the trans mount and Brad changed them to solid. It helped solid shifting.
I was told by the conversion designer (Jaide) to mount the bar solid to the body for correct engine placement. You would drop the body if "stock" isolation was added.
The engine bar to engine mount is sufficient for isolation. I switched to Polyurethane but I haven't got the car running yet.
If you're after more vibration isolation go for it. It will just add some more R&D.