As far as diffs go look for something like this:
http://cgi.ebay.com/Hot-Racing-RC18T...item255fcab5ac
It's the steel out drive diff for an RC18, you have to be careful as some of them such as the MIP ones are to wide for the ProPulse but myself, zippo and bart all have had ProPulses running these, and these:
http://cgi.ebay.com/Steel-Swing-Shaf...item2eb04b72f0
We also have steel gears on them making them basically unbreakable.
Hope that helps....