Kevin,

http://www.chevytrucks.org/tech/torquetube.htm

If you get the 3.55 kit from Patrick's, you might as well buy his installation kit. My 54 Suburban was relatively quiet before making the 3.55 conversion with the parts kit. It is noticeably quieter now. And, it cruises easily at 60+ mph (new original-style brakes and a tight front end).

Tim