If you're looking to stiffen up your suspension you might consider these endlinks with TPR bushings.  TPR bushings are stiffer than even polyurethane and effectively increase the stiffness of your existing sway bar. 

Bushings are sold per pair.

Rubber bushings are designed for soft rides and a long service life.  When considering a performance suspension the main goal is to limit sway in the body of the vehicle.  Rubber bushings are soft and will flex under pressure.  A common upgrade is polyurethane (poly) which is stiffer than rubber but still gives with pressure.  The stiffest of all is TPR.  TPR is a solid piece and feels hard to the touch.  It takes much more pressure to flex a TPR bushing than it does on an equivilent rubber or polyurethane bushing.  

• 1997-Current Regal, Grand Prix, Monte Carlo, Impala, Alero