ALL RIGHT!! FINALLY back on the road. After weeks of diagnosing and not driving my daily driver I am back on the road. Even tho it didn't make sense I REBUILT THE ORIGINAL DAMPER and THE VIBRATION IS GONE!!! Thank you, http://www.damperdoctor.com/ I don't know why the Summit replacement damper didn't work, it was proper application (1971-1992 360 external balance) and looked to be counterweighted correctly. To Summit's credit they did refund money 60 days after purchase and use of damper.

I do have a bit of droning left around 2700 rpm but I am sure it is my old mufflers and exhaust. I had 2 1/4" exhaust with Magnaflow mufflers, no droning when first installed. I took out the crossover with no change and just cut off the tailpipes just after the rear axle and removed crossover. Exhaust a little louder and droning reduced. I am going to replace exhaust system from headers back but have to repair a small leak in tank first.