A complete boneyard setup would be eaiest, if you can find one for a slant 6. All 1st gen truck PS boxes bolt up so you can grab whatever you can find,and source the brackets/pump/pulleys off a car if needed. There can be some issues when swapping parts. Different hoses etc. A 2WD box will bolt up, but the steering column shaft is shorter,and your manual is too long. You'll have to find a W series/Ramcharger shaft. Borgeson makes cut to fit shafts with U-joints,a worthy upgrade as the coupling pot at the box is usually shot. You'll need a W series PS steering arm.
Having said all that the stock setup has pi$$ poor geometry. How about a crossover steering conversion? Check this out.
http://ramchargercentral.com/index.p...owtoshow;id=21 There are a couple threads on this so look around.