The 2000 Sierra 1500 has a 8.25 ifs front ring gear and a 10 bolt 8.6 ring gear rear. The 8.5 ring gear is still used in the new housing though so you're correct. There is specific master install kit for the 2000. You can call me if you have anymore drive train questions or need help placing your order. 800-337-9005 x5123 Morgan