RCM Revo v3 1/8th diff: E-revo mod requirements?

[simplechamp]

The description on the 1/8 v3 diff case and diff for the Revo says it requires some modification of the E-revo to fit. Can someone explain what this will require me to do?

Also, if I buy 2 of them will that be everything I need to swap out both diffs to 1/8th scale version? My drivetrain is stock with the stock Traxxas driveshafts. I would like to get CVD's all around but can't afford everything at once, and would rather get the diffs first.

Thanks!