If I am following your question correctly, I believe that because 00 - 02 Dodge 4WD 2500 & 3500 diesel pickups came with Dana 60 front axles equipped with odd ball/odd duck 32 spline axles. These may not be compatible with "free wheel" front hub assemblies that typically are 35 spline. Dodge REALLY cheaped out and screwed the customer on this in order to cut the cost of these year trucks and make more profit.
I am in the process of installing an Eaton TruTrac in the Dana 80 rear axle and wanted to install an Eaton TruTrac in the front Dana 60 but the TruTrac for this application is made only for 35 spline axles which GM & Ford have but Dodge screwed the customer on. The ONLY streetable front traction device made and available for this axle to my knowledge is the Yukon Dura Grip limited slip differential.
Yes, I could change over to 35 spline axles which is VERY expensive. A Spin Tech hub system is about $1800 and a set of 35 spline axles, bearings, seals, and other change over parts/materials is not cheap either, prices vary depending upon the axle sets and sellers.