Originally posted by The Black Kat
I know...but where do I get/whats the part number for one?
The lightweight outdrives alone are like $17 
If you've read thru some of the previous pages, you'll have known
that Tamiya does not sell any EvoIII diff kit - need to build it from parts.
Get:
1x TA04 ball diff kit
1x EvoIII outdrives
1pr F201/EvoIII diff rings
2x 850 bearings
1x EvoIII diff gear
For your front diff buy the BLACK outdrives.
The white (dearer) ones are too brittle.