New 408/727 Vibrations

A "gold star" to everyone who said to check the timing/ignition, but thanks to all who replied. I checked all of the things that were mentioned here but what finally eliminated 90 percent of the vibration was backing way off of the timing and reducing the vacuum advance in the Edelbrock Pro Flo 4. That system cannot take much timing, which boggles my brain given how advanced the system is supposed to be. Though I am not near as knowledgeable as many of you on this site I have still built several small block Mopars and a couple of Ford truck motors, never a timing issue like this but I'm going to start a new thread reference the timing, thanks again to all who helped, it's much appreciated.