[RocktimusPryme]

I dont think there is a high chance this is your problem given the tests you have done, but to give everyone food for thought. Im fighting a similar issue with vibration. I read a review the other day for the M/T drag radials that I have on my car that says "They balance poorly and rattle your teeth out"

Then it occurred to me that I have only had those drag radials on the back since I started messing with my pinion angle. Before I lowered the car I mostly had the Rally II wheels with generic street tires on it. So Im going to swap back to street tires on the rear and see if it changes or eliminates my shake. Maybe my 60 MPH shake has been tire balance the whole time.