You can do whatever you want to your car. Pull it out of the driveway, though, and you're at the mercy of laws that vary from state to state. You better watch out for your suspension, too.
Cops love pulling over tricked cars with added suspension and good shocks.
The car can ride too low or high from the ground, and that can mean a ticket. It depends on the state. The same goes for wings on the back of the car. Legal in one state, illegal in another. The aspiring road warrior needs to know local regulations.