I have a F-350 super duty crew cab dually so far i have ripped out the rear seats and shaved off the rear doors, the front door handles and the tailgate and smothed the the body so its almost like silk. I have put a speaker sytem back where the rear seats were but now i want to lower the truck with a hydro system so it will rest on the ground. I want to know where i could find a hydro kit so i can raise the truck up when i want to go for a ride. I dont want to scrape my underbody up.

You'll be much better off with airbags or air-ride, since you'll have an enjoyable drive compared to the bounciness and rocking of hydros. Plus, theres application specific kits for airbags for your truck.