See if Energy Suspension or Prothane make a graphite-impregnated poly bushing for your application. Regardless of what bushings you end up using you will want to use a silicon-based or silicone-impregnated synthetic grease; Redline, Royal Purple, Mobile 1, and Neo make this type of grease. This grease is very durable and "clingy" so it doesn't wash out with water and your bushings will love it; you can also use it in ball joints and tie rods too.