You can modify stock motor mounts by adding bolts through the middle. That way you benefit from the rubber dampning the vibration but the bolts keep the rubber from stretching under torque so your sidepipes don't hit the body cutouts. I had that problem and corrected it by modifying my motor mounts. My engine is an FE but I assume you can do the same thing with small block motor mounts. Here's the details from ERA's website:
http://www.erareplicas.com/427man/en...tmod/index.htm