Only use GM 5 pinion planets if you are going to upgrade them. The after market ones are total junk. If you are 4wd a good billet output shaft is always a good idea. Not sure if you plan on building this yourself but buying a built unit from a well know company might be cheaper in the long run. As mentioned above those are the parts that should be addressed if you are building one. Also you should upgrade your plastic accumulator pistons and a new separator plate is always a good idea. Vince