Like Linc said, you still have to drill the ring gear t o accept 3mm screws. I can tell you that it's a pain in the ass to drill them unless you have a drill press. Traxxas ring gears are made of hardened steel.
Yes, those are the Nova alum diffs.
Here's the FLM diff drilled out to use 3mm screws. No drilling required. You can get a pair for $60 plus shipping.
http://www.2coolrc.com/detail.aspx?ID=93