By a Banks Hig Head Actuator for about $220 straight from Banks. They give complete instructions on how to install including preload.
I believe it said to line up the rod with the center of the pin, then tighten 6 more turns. This a little subjective, a mine turned out to have a little to much boost and turned on the SES light. No biggy, just add another turn and test.
Note: I did have to fill the end hole of the rod with an insert, becuase my pin was smaller than their hole. I also had to grind down on side of the rod, as it was thicker than the stock one. /ubbthreads/images/graemlins/sleepy.gif