Can't do it with a Saginaw style box. You'll need to get a new orbital valve and adapt it to your steering shaft...after figuring out how much flow/pressure you need to match the bore and travel of the ram. You'll probably want to change out the stock pump for something a little more robust too.
When looking the orbital, definitely go with a load-reactive one if you want the wheels to be self centering (dependent on alignment settings)...the one that most folks use is by Sauer / Danfoss. Also you'll have to get used to the fact that you won't have a "center" on the steering wheel - some fluid flow past the bypass and seals in the ram is unavoidable, so you'll generally have a different number of turns back to center (this will screw with the blinker switch etc. if you keep the stock column).
You'll also need an inline filter, reservoir, and cooler to keep the fluid from getting too hot and breaking down.
PSC is a good company to go with to get a complete package...