Oil shocks is your first bet. An esc if you don't have one. A good battery, and some foams for your tires may help a bit. A good strong steering servo and front servo mount is also agood idea.
A chassis kit with 4 links from CPE is probably your best bet.
However you can use the stock chassis with a 4 link kit, just see if you can get one of the ESP lower chassis braces. Il'll help keep the plastic tub chassis from breaking.
Dremel tool, or drill and files are going to be needed as well to do some ''customizing'' if you plan in keeping the stock plastic tub.