If you are getting something that looks like:
(top left) that includes the cases, then you wont need to buy anything else to fit them- they work with any normal bulkheads for the maxx trucks.
All you might need to do (besides the output shaft/cup change-over) is get some diff fluid/ oil, depends whats in there already ( I use 7k front & 5k rear, fairly standard starting point ).
If you use the stock type center drive shafts, you can use this:
http://www.rc-monster.com/proddetail...rcmrevocoupler
on the input shaft of the diff to connect it to the drive shaft, or there are special drive cups that work with the larger 8mm shaft if you want to use center cvds or dog bones:
http://www.rc-monster.com/proddetail...RCM8mmdrivecup
(HotBodies also sell similar items, thats what I used).
