8 3/4 posi unit change

dewsky said
I currently have an 8 3/4 with a 489 case with a set of 3.91 gears and a posi unit installed. I am wanting the make the car (75 Duster) a bit more friendly on the highway by installing a set of 3.23 gears. I have a complete rear end out of a D200 with a 489 case that has the gears, but it does not have Posi. My question is, how hard is it to swap the posi unit from case to case? I dont know, but I believe it's a stock unit with the posi.

oldkimmer said
Yes, but they are exactually the same unit. Kim

I have a stock 8 3/4 rearend and it has shims in both ends of the axle housing I'm putting a posi track 8 3/4 489 case in it do u know if I have to reuse the shims or not and if I do where do I need to put the shims at I'm new to this set and have no clue can u help me out with this situation