If you get the chance to get them cheap keep an eye out cause they go for about 650-1200 for the auto 4.5 or 3.9 and 800-1600 for the 4.11. They are the lightest production diff and one alfa guy has weighed a Hallibrand unit centre and housing and they come out to be the same only 3000 cheaper and with the ability for 400 hp as seen behind a sydney drag ke25 corolla that runs a big boosted 13b turbo and this guys done more than 500 launches with out any complaints or anything. He has a carshop tuning business and website with a lo-cost Delco injection software.