if you want a granada to get the bits from with "standard" ratios then you need to buy a pre 94 car

your potential purchase "should" have the 3.64:1 diff, same as the 2wd cossie and it "should" come with a 7.5 inch diff

if you want a 7 inch lsd then you would need to find an xr or cossie 4wd rear diff which are all interchagable and will fit in the same beam you are thinking of using