Answers: I would go with rpm arms with trutrac in the rear. Get flm chassis if your just going to bash, get a g4-maxx if your going to race if both you need to decide on your own both are good chassis. Traxxas cvd's will work with 1/8 scale diffs but you might have to figure out different deeper output cups if they are not long enough. UE is Unlimited Engineering
http://www.unlimitedengineering.com/cgi-bin/store the best parts money can buy but alittle pricey and alot of stuff is not being made anymore. Better off buying used on the bst forum. UE cvd are the best but wont work with current later model knuckles.