The ratios are different though between the 2 and 4wd riffs
3.64:1 and 3.62:1
Not really enough to fuck the transfer box but you need to be aware nevertheless
The 4wd rear beam uses the smaller 7 inch diff which is actually much smaller because it houses a 7inch set of gears inside while the 7.5 inch diff houses, as the name would suggest, a larger set of everything
The output flanges are also bigger as they have a pcd of 108mm which only the 2wd cossie cars came fitted with, the 4wd cars came with 100mm flanges the same as the rest if the rwd ford range from the Granada and the sierra and the escos
The shafts are also thicker as well as the flanges on the hub ends
The beam plate is also welded in a different place so that the diff can fit but seeing as its only one place where it differs you just need to use a longer bolt and make a spacer to fit it up