stock diff is fine. i packed mine full of putty so its locked. works great. first get a good set of shocks. i bought the tamiya works set for the mini. (i also bought the mk1 rabbit as im a vw head). get the aluminum steering set and the aluminum uprights. and a bearing set most importantly of all. go look on this site here:http://www.tqrcracing.com/shop/produ...&p_keyword=m05

they will have everything you need to hop it up. but, if your going to race in any of the tamiya championship races your gonna need to stay all tamiya hop ups. but check the site i suggested out. fast shipping too. good guys in socal.

sorry didnt read all of your post. just scanned and trying to help. lol. you have a good start.