So I have been looking around, and it seems like the lst/aftershock diffs can be had for about 20 bucks each. And Losi makes a heavy duty diff cup to that looks very sturdy, and comes as a complete kit...
IIRC the heavy duty case is standard issue, not an upgrade?
They were not in my aftershock, but i will pull the exploded diagram of the lst2 and see if they are in there. I use the Nova RC al cups in my Aftershock, but these Losi heavy duty cups are cheaper and look to be just as good.
Heres some other cool parts for the diffs, TiN coated gears should last a while, but are not cheap...