Shake Shake Shake

My 340 has a shake that I can't seem to tune out. I wonder if anyone has input after watching the video. The engine actually runs really well despite the way it sounds in the video. It's an intermittent shake that you can clearly see by looking at the air cleaner.

The motor is pretty low compression 9:1, cylinders cut .040 over (built 20 years ago low miles), Comp Cams 270H, Mopar Performance electronic ignition kit, Carter 4966 on an Edelbrock LD340 intake with Edelbrock RPM heads.

I've eliminated the carb as the problem as far as I can tell by tuning and even trying different carbs. There are no vacuum leaks at the intake or carb base.

The problem seems to remain, regardless of where I put the timing and advance. Currently the base timing is at about 15 degrees, and read about 35 total at 3k rpm.

https://youtu.be/ep-v-J5DJVY