Only the higher spec dohc cars had rear discs. If it has rear disc, chances are you have a 7inch open diff. Use a xr4x4 lsd or cossie 4x4 diff as this will fit your beam. And the drive shaft flanges will fit fine. If you do have drums, then all you need is the drive shaft flanges and you can swap these over easily onto your original shafts. So one end will be push fit and the other end will bolt up to the diff. The diff ratio is different (3.64:1) so it does blunt the acceleration abit as i have done it on mine. A 2wd 7 1/2 inch would be even worse as these are 3.62:1. The 2wd casing will need to be modified to fit a seven inch rear beam as well. PM me if you need more info as I have done all this recently.
HTH