As per their web site you can use stock springs and shocks. You have to remember that larger springs and shocks do not give you more travel, it just gives you a higher ride height. You can acually have more travel from stock gear than with most aftermarket stuff, most aftermarket will be heavier which will not compress as far and basically not allow you to travel as much.
If you plan to due some serious off roading on a weekly basis, this wouldn't be a bad way to go, but remember for the cost of this you can do a lot of other upgrades.
As I was told a long time ago when I used to race R/C stadium trucks... Driving and experience will go a long way and a lot farther then any aftermarket upgrade that you can add. If you spend more time and money driving, than you do on upgrades, you will be a better driver and the upgrades will help more later on.
Just me $.02