We use a lot of McGaughys products, and they offer a drop spindle for your truck. In most cases, when going to a drop spindle you also have to convert to a disc brake setup. This can be done in 6-lug though.
We have out Pro1 brake conversion kit, that uses all McGaughys parts and is available in 6-lug.
http://www.azproperformance.com/Pro1...60-72-C10.html