We need the "beating a dead horse" icon on this forum.
It wont do a damn thing. Its a brick and weighs a lot, and wont get "good" mileage no matter what. I also did the "maual hub conversion" on a 1975 K5. It had a full time NP203 Transfer case. I put in a kit that made the Tcase part time, and added warn manual hubs. The only difference was that the front tires didnt wear as much, but the rears probably wore down more. Mileage was the same.