main differences between the above two boxes - depending on which car they come out of, they will have wither a 3.6 or a 3.2:1 1st gear, and either a 3.9 (most common) or a 4.1:1 diff.
in the box i have put together for my aw11/3sge is a s54 - it has the 3.2 1st, 4.1 final drive, and a lsd!! you have to know where to find all the parts to build one though!!!