Yeah, full hydro steering is very illegal on the road.
Hydraulic assisted steering, on the other hand, is legal, and quite helpful if you drive a serious off-road machine.
With hydro assist, you retain the factory power steering system, along with the mechanical link to the power steering box. So, if you blow a hydraulic line, or something, you will still be able to steer your truck.
There is a mod you can perform to your stock power steering box so you can use your factory power steering pump etc to run the ram.
Search coloradok5, or pirate, and you'll find tons of useful information
