I traded tires
When I was reading your opening post I was thinking your front tires must be way out of balance. The larger the diameter of a tire the more leverage any off balanced mass has to work (torque) your axle.
Get your tires balanced and let us know if that helps-
Also, are you using any wheel spacers? If so the wider the spacer the more affect an off balanced tire will have through feedback of the steering wheel.
really dumb question, but you did remember to put rubber or urathane bushings in your front spring pirches, right?
BigMike