Hi Mike. I Replaced the factory SPF rubber bushings at the front and rear with solid machined aluminum bushings at the frame and polyurethane at the links which supposedly has the same result as upgrading to a larger bar. Quoted from How to Make Your Car Handle. "An .080" bar with solid bushings gave the same effect as a 1.00" rubber mounted bar".
From
www.bicknellracingproducts.com I'm going to replace the front bar with a 1 1/8" tubular splined bar with solid aluminum bushings and 3/4" broached aluminum arms and rod end links. In a spring rate of 150,200 or 300lbs? I still don't really have a base line and would be interested in your results as to the spring rates.