You dont have to go to a custom shop. Go to Pep Boys. Autozone, or anywhere they sell car parts maybe. If they dont have the answer ask if they know where you can get one. Try ordering a pair over the internet maybe. There might be a site with instructions or you can have them professionally installed...
Joe,
Pick up a few back issues of Sport Truck Magazine.
They used to do installs of lowering kits, 'C' notching the rear frame, and everything you ever wanted to know about.
Have it professionally installed or at least have very good instructions. You dont wont to end up doing it wrong and messing up the balance of the vehicle...