[Rick 427 Cobra]

As Chris and I have said, check the motor mounts. They can easily be installed incorrectly. They will bolt to the engine and frame, look "good" but be wrong! I've done it.
And don't just look, compare on other cars.
ERA builds a quality product. All this monkey motion about chaining, bolting, slotting, shimming, etc is bad. This sounds like the most common problem of all, builder error. We have all done it, be honest.
As far as the mounts "settling", gimme a break. Those mounts will go a 100k.
Hopefully Bob will chip in soon.