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.
