not sure if this is still active but here's my 2c
vl diff's do not fit unless u modify the mounts, but there is no point in that as others have previously said r31 diffs hold up just fine. i have had my 31 spooled for more than 4yrs and never broken an axle now its turbs and still holds up fine with constant thrashing
and to break a 28 spline axle it either cause it was already stuffed or you actually have the power to break em