In regards to the diff, md005 is the factory option. However, ball diffs from GL racing and Atomic should also be compatible with your ma03. I used my AMZ's ball diff in my 030 EVO with no problem.
The other option will be the IW04's gear diff since IW04 shares a lot of parts with MA010. I have no experience with IW04 though, so I have no idea if the diff is smooth out of the box.