I see other regions that have listings for places locally that are helpful to Viper owners and I'll share one here for the Twin-Cities area.

Libson Twin City Auto & Truck Parts and Service (Dana-Spicer Dealer)
I had a 01' differential re-built by these guys and it's still working great. Labor was just under $700 for the rebuild parts and labor...New Gears would be extra $$, and they only install gears ordered through them.