Originally Posted by CLEVELAND JUNKY
I would find a disc brake diff from either a V8 XD or a V8 ZJ fairlane, both are 4 pinion and very strong. All ZJ V8 fairlanes were disc brake rear and there are plenty in wrecking yards. Both of the above^ diffs will bolt in your XB.
You will have to remove the residual valve in your master cylinder when installing a disc rear end in place of a drum rear. You dont have to change master cylinders, just remove the residual valve. The valve is located behind the big nut on the front of the master cylinder, just undo the nut, remove the valve and replace the nut easy. Ford diffs - www.fordforums.com/attachment.php?attachmentid=12248
i removed a LSD centre from a 351 XD (supposedly ex-cop....) and it was a 2-pinion 25-spline centre. Only thing was i think it may have been originally a 6 cyl...other than that i do remember reading in SM that the 351 XD's and v8 XE's were the only ones in that falcon range that came with the 4-pinion.
though the easy way to check is by counting the splines as i think all 4-pinions have 28 splines....
 definitaly agree, a 4 pinion LSD (in most cases) will be all you need.